Custom animations in TF2

[Mystfit]

Hey guys, I'm just getting started with XSI for animation, primarily for developing custom animations for machinima. At the moment, I'm currently focusing on making some custom animations for TF2 characters but I'm having some problems with animating.

I've decompiled the Heavy Weapons guy and loaded him up into XSI so I can play around with his bones and make a few skeletal animation smd's, but it's quite hard to grab onto the bones I need at the moment. My question is, can I use the Biped guide ... thing for the animations rather than the bones which decompiled with the reference smd? I'm fairly new at rigging and pretty much anything relating to XSI, but do I have to create a new rig for the Heavy if I want to easily animate him?

And I've managed to get some animations working in TF2 as well, shame that somehow the decompiler manages to screw up all of the TF2 animations which are 90 degrees on their side, turning the Heavy into a meatball. Is there any way around this or should I blame MdlDecompiler?