Well, so far the only one that has made the list is Heaven Can Wait (We Hope!!!)
Read my post again--We All Fall Down in Taxing and Mayhem also makes the list.
One thing you can do to eliminate levels for which at the default RR, you can't even get the last lemming entering the level on time, is by the following rough calculation:
((99 - RR) / 2 + 4) * (number of lemmings - 1) / 17 = number of seconds elapsed when last lemming enters
(RR needs to be odd in the formula above. So if RR is 50, use 51.)
This is not a totally accurate calculation, and obviously it takes time between last lemming entering the level and exiting it. However, if the number of seconds it takes is much more than the level gives you, then you know it's impossible.
(Some level doesn't require you to save 100%, so "number of lemmings" in that case would be minimum number of lemmings you need to save.)
Using this formula for example, you'll find that at the default RR, it'll take more than 2 minutes before the last lemming can enter in "Just a Minute" and "Just a Minute (Part 2)".