While I would love to convert certain powered 2 rail models to three rail, they would
all be models for which no three rail versions exist. (there are a lot of those) I would not go through the hassle of cutting up something, if I could find a model of it, and the chassis was close. If detail is not good, I would tackle adding that to it, and not have all the potential problems cited above. It sounds easier just to build up a brass detailed shell for an existing three rail chassis. (obviously, that demands soldering
skills, but starting with a running chassis, you are more likely to end with one)
