you should only need the north coil, neck side of the middle humbucker in single coil mode. you could also just rid yourself of the neck and bridge pickup, they are useless in a jerry rig as well!
all kidding aside, this sounds pretty spot on. i am in the camp that jerry used humbuckers more in JGB then the GD because of only one guitar in the band. he did use single coil mode in JGB, but i hear humbuckers from time to time in JGB. could be just me, but he has those coil tap switches on those guitars for a reason.
Rum Runners Rock!