Played around with the shift point and the adjustment screw was pretty much tightened clockwise. I adjusted the shift adjustment screw and the times for the 2 NiMh's in series was the same (3 minutes of peak running - however, 30 seconds of that was me having to run and flip the truck back over).

I also have a 2s Maxamps 6000 and it ran for 17 minutes.

Oops, sounds like the 4S is done charging, let me go test the new shift point.