Yes, Rough 8 is even harder than Fierce 15, where I am back to 88% .

Some selected replays attached and some comments here:
Fierce 4: Your fixes created a new solution, though it's now likely to be closer to the intended one. I hardly ever found such wasteful (but necessary) uses for diggers.
Fierce 11: My solution still works and got even nicer. Though I wonder whether the skill changes didn't simplify the level, as one has fewer possiblities to pass the obstacles.
Fierce 12: Were you aware that one can easily omit one builder in my solution as well? There is now a certain part in my solution where the large number of lemmings is slightly annoying.
Fierce 15: I am confused about this one. My usual approach can be modified to work as well for this version (and saves again 88%). But I had to change the part I thought you referred to when you wrote in PM, that I solved about half of the level in the intended way? Btw. I liked the previous version better, because it felt cleaner.

As for those, who wonder how I got so far in Fierce:

The officially released and the test version use the same level codes and cheating was allowed in the test version .

A very interesting solution with a totally unexpected use of the bomber . As of now, I am undecided whether to keep your solution. On the one hand it's probably not the best idea to make the level even harder and having two interesting, but completely different solutions would be a good feature of a level in a community level pack. On the other hand, your solution is much more linear than mine and misses some other features as well.
The easiest way to remove your solution would be to change the number of lixes to 100 (or even 200) and still allowing to lose only four lixes.

Here is my first proposal for inclusion in project Capybara. The level is meant to be very hard (at least once the tons of backroutes are removed ).

Attached some solutions to levels which had backroute fixes, though I guess all of them are rather close to the intended solutions.

Slipping: möbius' new version of Slipping (i.e. the tseug remake) is quite a bit easier than the original Lemmix level, cf. attached solution. Imo Top Gear and Lixes in Motion are more interesting puzzles than the current Slipping Again and Three Days.

Tinker Tailor Soldier: You mention in the first post that you consider fixing the RR at 50 (to remove a backroute?). Then you should either relax (or remove) the time limit or reduce the number of lixes. As it is, there is not enough time for the very last lix to appear and walk unhindered to the exit (at least with my solution). I am not aware of any solution that the corrent time limit removes, but that doesn't mean anything.

Division of Labor: I remember that on my first few tries, I took about 10-30 seconds to long. So the time limit here definitely removes some solutions.

Quote from: Nepster on 2014-06-14 12:50:04

S2L22 - Hard to Port!: There is a backroute which is much harder than the intended solution

Are you by any chance a married bachelor? 

Yeah, kind of. The point is, that I believe that möbius made the level with one specific theme in mind, which can be circumvented using this approach. Moreover my solution is harder mainly because one needs some very precise skill assignments, so "much more annoying in its execution" instead of "much harder" would have been a better descrption.

I (nearly) played through all of the levels in V3. Most of then were quite fun, except for some long and repetitive ones (like "Path to Mahimah") and the two levels I would put in the category "fool the player" (namely "Puzzlin' Evidence" and "Nothing Gold Can Stay"). Apart from them:   
My favourites are: Going down, Another funeral... (at least after simplifying the digger placement), Five for Fighting, Suspended Animation and the last three levels in Heinous.

Attached is a bunch of replays. Names like "S2L13" stand for "stage 2, level 13". Most of them should (hopefully) be rather close to the intended solutions. Those I believe are not (or have other interesting things going on) are mentioned below.

S1L1 - Lesson 1 - Block: Good blocker tutorial, but imo not trivial enough for the very first level. You have two hatches, lemmings will die when left alone and some traps are around...
S1L3 - It's A-Bashing: If you bash too low on the bottom right end, it's impossible to still solve the level. I don't know if that's a good thing to have in a tutorial level?
S1L11 - Send in the Lemmings: The ceiling route is trivial and uninteresting.
S1L23 - Workin' on a chain: Way too hard for Friendly. There is a 1-pixel gap in the vertical chain on the right, which can have annoying consequences. And I doubt my solution is intended...
S1L25 - Ice Cave: Boring - just dig down and then bash!
S1L26 - Lemming Overboard: In the rocks in the middle there is a 1-pixel gap that will trap the lemmings between it and the steel wall on the right. Depending on whether this is inteded, I would suggest to remove this gap or make it more visible. On the top platform at the right I noticed that you made it slightly thinner unter the rock. You did this probably to disallow digging down and then bashing along the platform. Right now it isn't a priori clear that this won't work, so maybe make the whole platform several pixels thinner?
S1L30 - Oh Lemming, where art thou?: I was slightly disappointed that there was no repeat for this level with a reduced skill set.

S2L6 - And the Long Shadows: No need to bash through any one-way-wall, cf. replay.
S2L12 - The Path to Mahimah: Way too long and not really intersting.
S2L17 - What's for dinner?: Not my type of level and more of a Friendly level.
S2L20 - The Six o'clock Rush: Good level, but too hard for Flapdoodle.
S2L22 - Hard to Port!: There is a backroute which is much harder than the intended solution, but doesn't need the blocker.
S2L28 - Loophole: My solution needs a Lemmini-only behaviour, which I consider a glitch.

S3L1 - The Icarus Agenda: At the bottom of the one-way-wall there is steel that goes way further than the graphics suggest. This had me placing the miner wrongly on my first try.
S3L5 - Eight Slippery Lemmings: How did changing the RR make the level easier? (OK, at least when considering only my solution, which is likely to be unintended)
S3L6 - Lemmings in Motion: The hardest level in MobiLems. Not yet solved (and neither the Lix version).
S3L7 - Going Down?: Have some spare skills...
S3L16 - Another Funeral...: The hidden steel makes the digger placement complicated.
S3L17 - Puzzlin' Evidence: No fan of this level - the solution is rather easy and uninteresting, but you never expect this to work.
S3L19 - It Takes Time to Build: Backrouted.
S3L24 - Road to Nowhere: 98% without the bomber possible.
S3L25 - Babylon Fading: Not yet solved. But this level seems the same as in V1. What have you changed?

S4L5 - Nothing Gold Can Stay: Not a fan of such levels, especially with what you did to the exit object.
S4L6 - Every Which Way But Loose: Backrouted.
S4L11 - Honey, I have shrunk the levels II: 100% possible.
S4L13 - Suspended Animation: 93% possible.
S4L21 - Eye of the Needle: The second builder has to be placed rather precisely. It would be easier if the exit platform would be 1 pixel lower or if the steel flag starts a few pixels higher.
S4L23 - Tres Hombres: The builder placement needs to be extremly precise. Is there no possibility to modify the level to allow for one or two pixels leeway?
S4L24 - Lemmings with the Golden Gun: 91% possible.
S4L26 - Passing Engagement: Backrouted

I'm still not confident Picard Maneuver is free of backroutes.

If it helps you, here are the three (somewhat similar) solutions I know of.
(and you might wish to check the attachement in you post as it seems to be an empty txt.-file)

On that note, if you are finding potential solutions that you can't execute but think may be possible, please feel free to let me know anyway, ...

I have two approaches that need slight modifications in the game mechanics to work (so no need to worry right now, but if a future release changes them...). As I haven't saved replays after convincing myself that these solutions don't work, here are only the two specific game mechanics in question:
- Bombers walking down a miner tunnel create a hole that turns other lixes around. If this would also hold for bombers walking up...
- Bashers are somewhat slow with their first stroke. If they would be as fast as in Lemmix...
If you are interested I can make replays (at least without the RR-fiddling needed to make them actually work).

"Dances with Lixes": Another (easier) solution not mentioned in geoo's post, which should be hard to remove as it allows for many variations and doesn't use all skills.
"News Struck at Ten": If my solution is intended, then this level is way easier than rated.

Mod Edit: Restored attachments.