I don't think that will work considering Jimmys skeleton was made for a smaller/shorter model. For example, if you changed a Huge character such as a Prefect or a Jock and used them for Jimmy's skeleton, he would be all squished, weird jaw line, clipping occurring etc. you're better off changing Jimmy's height and using a larger model, like a Cop, Prefect, Adult, Jock, Prep etc.