Okay, so it seems what's actually going on here is that there's no head check at all in L3D; the timing in that particular level just worked out that the peak of the jump coincided with when it looked like the lemming hit its head. Loap in fact behaves the same way, too, once an actual head-hit is set up.
However, what will often happen is that once the lemming gets far enough into a block, the wall check triggers, causing the lemming to fall down (at normal faller trajectory, with the slight forward momentum that occurs for most fallers) and turn around.
I don't think this behavior is ideal, and am thinking that this should be a case where Loap introduces an intentional physics difference from L3D. I can see one of two desirable behaviors here - either the lemming (immediately upon hitting head, rather than waiting for a wall check) falls down without turning around; or the forward momentum continues but the upwards momentum acts as if the lemming has reached the peak of his jump upon hitting head. (A third possibility is SPLAT!, but I'm not too keen on this one.) I have a slight lean towards the first option at the moment, but this is not a strong preference.
Test level attached. Filenames are set up for Loap's test levels folder; if you put these (without renaming them) into DOS L3D, it'll replace Fun 6.
