Regarding stairs, I think new collision is a bit wonky with them. This is one reason why I'm using the old AABB style collision with the c_instructions. It just works better with this particular code(no camera jerks/stuttering), plus it's faster. One trick with stairs is to make all of them passable and include an invisible ramp where the stairs are located. It gives the illusion that the player is ascending the staircase but uses the smooth slope instead of the jagged stairs. It's a cheat, but it works for the most part. It can work even better if you make a stair climbing animation for the player, but that would require some more work and timing issues. I suppose you could place a vertex(or two) on each stair and make sure a specially placed vertex on the bottom of the player's feet connects with the stair ones. This would keep the feet on the stairs, but I think this is overkill and really not needed at all if you're doing a fast paced game.

I'm going to investigate the alternate blending code from earlier in this thread. It's much easier to read and appears that it would easier to add new modes to...plus it's just plain shorter. I think I'll do that first thing.

Regarding your snippet...where do you place it in the code?

Oh, and jcl has apparently fixed the enable_polycollision problem. The newest beta feature is allowing AABB to influence the trace_hit. I'm glad I reported it, now. Perhaps, this will also allow Intense Pathfinding to also use this setting, too. Good news if true.