Just looking at the remaining levels of Original Lemmings. It's harder to execute these solutions when some of the replays disappear, and also without specific resources on what exact implications need to occur to pull off these glitches. I have made some good results here, but some levels I'm struggling with too.
Fun 15 I can confirm is improved to
4 of each. Replay attached. And yep, there is sliding involved here.
Mayhem 18: Improved to
6 of each. This solution combines elements of the 3 builder replay with the old 8-builder's data for the skills used on each side. In order to distribute the skills evenly it turned out I needed to combine the 3-builder's left side solution with the 8-builder's right.
Taxing 4 requires more sliding obviously, but where to do it will take some guessing. Apparently I can't see the 1-builder or the 7-skill solution on the forums anywhere
According to the 7-skill post you'll need to execute several release rate changes. Result at the moment stands at 5 thanks to a 1 builder solution.
Mayhem 14 is easily doable with 16, but can be done with less. Apparently the 15-skill replay uses 1 bomber, 1 blocker, 4 builders and 2 diggers, which adds up to 8, and involves the glitch that doesn't work on Lemmix replays (And therefore, I don't know how to pull this off). So far I can't tell which 7 other skills are required to make the solution work.