John,
We run the batteries forward, and inboard like I mentioned before. Weight is added in the spot beside the motor that you used. We have not tryed to balance side to side , we just set the tweak even, with a balance beam.
We run foams too, so our set-up is much stiffer than yours.
Usually yellow front and purple rear springs, 60 weight in front and 40 in the rear.
Ted