I'm planning on buying a couple of SSL-3's to put in my HSS strat. (JB in the bridge) Is it necessary to get a RWRP for the middle pup or can I just wire the black to hot and the white to ground?
that will reverse the start and ground wires which will put it out of phase and probably not what you want to do. you want reverse wound and reverse polarity, out of phase twice so its back in phase but also cancels hum.
or you can not worry about humcancelling and just get two normal ones