I never attach collisions to a mesh. I always create a pivot, offset the pivot and attach collisions to that. I actually like having models with their feet at 0,0,0. It's how I do my own my own models. The great thing about using a pivot for collisions is that you can have two or more per character. Which is great for doing show-off stuff like making your character automatically duck ( collision with higher pivot but not lower ) or jump ( collision with lower pivot but not higher )