Regarding the angular momentum glitch. Is the math wrong somewhere or is floating point demons the culprit? I have a bat-guano crazy thought that could address both and don't even know if it's practical or even possible. The idea involves pointing forces applied to the physical parts in the direction of the origin of dummy objects corresponding to the same objects on rails (a duplicate in empty form, a collection of origins). Instead of trying to distribute momentum manually this would use information from an on rails object to drag the craft and parts until they matched rotation speed (when the origins line up and become stable).
