Ok, "designing" is perhaps an overstatement of how JC turned the LP Sig into his own signature model. He changed the pup (not for the better though in my opinion) and the pup position slightly and the neck board is set a little higher giving you more range with the three point. At the time the Epi JC came out (and LP Sigs had long been forgotten), Jack certainly acted as if he had invented that bass from scratch, long thoughtful interviews and all.