Roman: thanks!

kbrown: You can get into all kinds of funky animation modifications with expressions. Last year I started doing some experimental Mel scripting junk with swapping nodes (through a UI) that modify my character's rig's animations to give it a different "behaviour"...unfortunately, I didn't have time to continue with the R&D for this, or polish it much...in fact, I only got as far as getting it to "work", but it was definately fun.
But another suggestion would be to not even bother using the "auto hip-centering" setup at all. I've found through past experience that (unless you add a switch into your rig to turn it on/off) it can be more hindering and annoying than helpful and useful, but I generally don't like automating things too much.
c.