Here's, for comparison purposes, Mike's conversion chassis. I can definetly see what you are talking about with angle of the rear axle. In comparison Mike's uses standard RC8T axles, no custom ones unlike it appears the Tekno conversion.
Btw, I would definetly suggest, as you are, the plastic chassis braces. I went through several of the aluminum rod braces, bent them up pretty good, and one set of the more expensive aluminum braces. I've switched to using the plastic braces as they give some more support but also flex a bit and are cheaper to replace.