I agree that the SR is basically a P body shape. But consider the Mustang design "innovations" that Leo presumably thought to be progress beyond the 2nd version P - he has a bridge that incorporates mutes and larger footprint, the pickguard on the E string side is oval shaped, and the controls are in a separate plate (Jazz hangover). The pup was obviously a cheap P vibe. And the Mustang is kind of a squished P shape anyway. Those are all carried over to the Stingray. The big slug pup and 3/1 headstock were things he came up with later, and those would be the innovations that weren't style related. 3/1 supposedly was to deal with dead spots, and the pup and preamp were developed in the era. The SR pup layout is mimiced by the G&L stuff, and I would bet if the tuner layout hadn't been copyrighted for MM, he would have done that on G&L as well. All the Fender designed basses are simillar, but to me the Mustang was the missing link to the SR.