Now that I've got Lemmings Revolution working on my new computer (thanks once again to GuyPerfect), I was able to find a new record:
Level 11-8 (Speedy Gonzalez): 100% (Previous record was 52/53).
The lemming that was lost in the 52/53 solution was the blocker that restrained the crowd at the top left while a lemming from below built a catch bridge to break their fall and ultimately hit the switch to drain the water. This lemming can be saved as follows:
1. Make him block as far to the left as possible.
2. The lemming that builds the catch bridge only builds just once from a pixel-precise spot, such that the lemmings from above will fall on his top brick.
3. When the blocker is bombed and the countdown reaches zero, he will fall off the left edge of the platform and land on the bridge you built earlier. He lands just before he goes off, giving you an instant during which you can reset him with a builder, which will ultimately get the top group to trip the switch.
The bomber resetting glitch has been used in numerous other solutions, so there is nothing new with that. The falling off the left side of the platform glitch is one that I've known about for a while (I once alluded to it
here), but I'm pretty sure this is the first case of it actually being needed for a max-% solution.
The rest of the solution is largely the same as the intended 52/53 solution. The only other tricky part is getting the timing right so that nobody falls in the water before it is drained.