Oh my
Congratulations!
Back on the old Lemmingswelt forums, when we were searching out all of the level records, someone (I think it was either ccexplore or tseug) came to the conclusion that 100% was impossible due to a builder shortage. I looked at the level several times since then and came to the same conclusion (a Taxing 16-like method to hold the crowd falls short by three builders). I never would have thought to do what you did!
I can't view replays, but I was able figure out the solution by studying ccexplore's screenshots and deducing where each builder had to be placed. From there, I was able to figure out on my own how to get the timing down so that the builders interact with each other properly to get the desired effect.
This is truly an incredible solution, rivaling the Lose 2 solution to Mayhem 10 and the 100% solution to Mayhem 2 in terms of difficulty. It makes my Mayhem 29 Lose 2 solution look easy in comparison. Well done once again!