Every custom player model i install is hunched over and i was wondering how to fix this.

lol your probably using 1.0 models ?

When 1.0 came out, there was a big race to convert 3.1 models over, so there was an over-flow of 1.0 player models.

But shortly after, the dev team implemented a new animation system [more blending, or whatever], so all those models stopped working right.

You'll have to have models compatible with the new animation system. Or figure out how to convert those models [decompile, recompile with the new anims and compiler]. There was talk about an easy converter, but I haven't noticed anything. Might be in one of the stickies.