Sure, I suppose I can do that, since you put all the hard work into the physics
The code is a bit messy right now, but I'll make a class for the test-bed in the next few days.
I put the neck in there because I'm eventually going to make a platformer with guns, and I didn't want any bullets to slip between the head and torso. Plus, how cool is it to shoot someone in the neck? :p I'll take it out for the test bed though. You're right, it causes a few minor problems.
The biped is modeled after a real person so I could get the proportions right (that was painstaking!). The mass, height, and friction should be fairly realistic too (I looked up values). I approximated the max rotations by how flexible I am
One thing though... I gave all the body parts a groupIndex of -1 so they don't collide with eachother... but when I create multiple bipeds, I guess they should all have a unique index. Should I require the developer to pass in a unique ID for each biped, or is there an easier/better way to do this?