So... would a small steel block on the top left of the structure solve anything? I'm more worried that that would create even more backroutes. Thin layer of left-facing arrows on the top?
Ok, check your e-mail for the latest backroute. It has nothing to do w/ your proposed change above. It has no collision timing involved, and in fact it resembles far more one of my earlier backroutes than those recent collision-timing solutions.
I don't know why I've overlooked it for so long, probably because it didn't seem like it would actually work out but hey it does.
This one actually saves exactly 28/40 and has more than half a minute left.
Don't think though that just because it's 28/40 you can eliminate it by increasing the requirements. It's difficult to say for sure, but I do have a few spare bashers left, and so it's conceivable that they can be used to help squeeze in 1 or 2 more lemmings. Of course it'd make things trickier I suppose.