in the SD Specs I can only find Bridge and Neck Pickups! Do I have to use a neck Pickup for middle position or are middle pickups just not on the list?
Yeah, that's the old series tele tone from the PRS megaswitch knock off ... outer coils in series (you gotta reverse the magnetic polarity of one pup to keep it humcancelling). I don't think PRS ever did that though, they did do the inner coils in series though. The John Petrucci model had that as a default setting in the middle position ... kinda sounds like a fat louder version of the bridge and middle position on a strat (kinda like), the old PRS CE series had that as the middle default also.
As far as single coils go, Lindy Fralin is about the only guy I know that winds (or at leaset does upon request) a separate single coil for the middle, if your into maximizing the tonal response of all the positions, that's the way to go.
Or you can mix and match other pups in that slot.