Goldberg Extra mods
Walt,
The mods that you are making will probably add weight to the tail group, so you will need to rebalance the model. The required CG is determined by the wing air foil and the resultant center of lift, NOT by the tail group configuration. For stable flight in most aircraft, the cg must be in front of the center of lift. You would rebalance using the SAME CG as recommended by the manufacturer as a starting point. From there you can shift the cg as desired to change flight characteristics, the further aft, the more unstabel in pitch the aircraft will be. Too far aft and it will not be controllable. I would stay with zero incindence for the horizontal stabilizer.
My 2 cents,
Jerry