There's a good chance your Starfire will actually be hum-cancelling in the middle position once you flip one set of magnets - seymour duncan antiquity sets are reverse wound as far as I know, unless somebody goofed at the factory. Flipping the magnets will reverse the polarity, and RW/RP = hum canceling.
On Franz pickups flipping magnets is as simple as the construction is almost exactly the same. But on Franz pickups, Todd pickups and small Guild humbuckers it's even easier, as our dear Hans Moust patiently explained to my *much* younger, greener self a loong time ago on the phone.
On those pickups it's easier to flip the coil wires coming from the pickup than on a Gibson-type P90, if you have a soldering iron.
The ground connection to the base plate is made by the little two-eyelet tab that screws onto the back of the pickup. Unsolder the two wires exiting the coil from that tab, re-solder them in reverse, and you flipped the phase.
The coil wires ánd the magnets being so accessible makes it very easy to make a set of Franz pickups hum-canceling in the middle switch position if you want, I've done exactly that on my guitars, and it's been a lifesaver in a couple of instances.