Improved Mayhem 10 to 29 skills. This may be the first time we've looked at this level specifically for this challenge, as opposed to just taking an existing solution from one of the other challenges.
One obvious thing to explore is ceiling route, but that turns out actually not great, the shape of the ceiling really works against you forcing you to use more builders than you'd like, plus it also costs a lot of builders to set up, at the upper area only, a holding system for the crowd--especially since the ceiling route takes up a basher, so you don't even have enough leftover skills to use 2 blockers (and still be able to free them both), you can only use 1 blocker. My testing seems to show that any ceiling route solution would end up using either all builders or at best maybe 1 less than all.
So instead, the improved solution here is yet another floor route building to the right exit, like the other two lose-2 solutions previously presented.
I'm still wondering whether maybe it's worth trying to use sliding glitch twice, the second time to slide the crowd up from bottom of the exit-holding pillar. From the one-blocker solution, we know there's one natural place that can be easily used to compress the crowd without using a second blocker (that you won't have enough skills left to free). But it takes multiple builders to later release the crowd from that location, which may well cancel out trying to use less builders by using sliding glitch.