Noisy Pickup Probs...

[Oakus]

Hello,
Hoping for some advice and guidance.
I just installed some S/D's in my guuitar. 2 H/B's at neck and Bridge, Single Coil in Middle; in a standeard 5-way switch config. with 1 vol and 1 tone control. The tone pot is Push/Pull so I can split the Neck and Bridge H/B's.

But seems overly noisy when I split either H/B or run them in the #2 and #4 switch positions. Also, I thought running in #2 or #4 position would hum cancel....but it's quieter when I just run the middle single coil.(I compared it with my strat in these positions and the strat's much quieter.)

Is this some kind of earth loop problem?
Thanks for your time. Oakus