Googling for what each position of the 5 way does... I assume something like:
Assuming position 1 is closest to neck:
1: neck pup (S)
2: neck + 1/2 of bridge (ie. 2 singles)
3: (middle) both pickups
4: Bridge, single coil
5: Bridge, full humbucker
I found the schematic on the Stingray 5 page of the music-man website. Very interesting.