I ran some calculations on an aero design computer program today and it says for aerobatics the cg should be 0.5 to 1.25 inches behind the wing tube so it sounds like you are going in the right direction Kieth. The same program yields 0.75 to 1.5 inches in front of the tube for trainer type stability. That tells me there is a wide operating range and I should design a mount that allows me to move the packs quite a distance. By the way it looks like the wing tube center line is just slightly forward of the mean aerodynamic quarter chord of the wing. The aero center of the whole plane is aft of there so the calculations sound reasonable.
Thanks for the inputs guys.

Jim O