Gramsci,
How does the Duncan mount into your TB500? From the messing around I've done, the mounting screws on a P-90 don't line up with the pickup mounting holes on a Bean. Is the Duncan maybe attached to the pickguard via a dogear cover?
Also, despite the fact that the ruling classes have won consent from the masses, thus convincing them that TB500 pickups are copies of P-90s, from what I've seen, this is a not the case.

The 500 pickups that I've seen up close are almost like glorified strat pickups: alnico 5 poles with the wire wound to 6k or so and then epoxied together with a resin sort of cover. The whole thing is mounted to a 1/4" base plate, making it almost a tele kind of pickup.
A true P-90 has two opposing bar magnets underneath the bobbin. The pole pieces screw down to come into contact with these magnets. Of course, isn't there another kind of 500 pickup, with plastic covers that you can actually remove and that say "Travis Bean" on them? I haven't seen these, and they may actually be P90 style.
David