What if you had a '51 p-pup where it usually goes and a jazz pup in the neck position! I've noticed on a normal PJ you can't solo the j without losing some volume, but if they are both single coil that wouldn't happen right? And they could cancel most of the hum if you have reverse polarity... it would act like a jazz and sound like a PJ! A '51 PJ :p that would be a sweet warmoth build :o

(P.S. Sorry if this is in the wrong sub-forum...)

I think you're in the proper forum- beyond that, w/a Jazz in the neck position, I'd call it a JP. :)
Slightly more seriously though, I always thought a pair of single-coils would hum unless they were balanced(both full-volume); this has been my experience w/my Jazz 5. Also, a 51 PU *where it usually goes* to me seems to leave little room at the neck, unless you mean right up against the neck end, like on some guitars.

Sorry I said the jazz in the neck... I meant in the bridge :o hehe just got so dang excited!

I wondered about this as well not long ago. Even started looking for a cheap 51 p pickup to try it, but then got sidetracked.

Do you have the parts and are you going to try it?