I try to install all my tanks right on the target CG.. or as close to it as I can. Usually that means the middle of the suggested range, or on the tube if that is the suggested balance point. In the case of the 28%, it was impossible to mount the tank on the tube or at CG, the center of the tank is mounted slightly forward. I balanced the plane empty and full to see what the difference is. Not much with a 20oz tank, the cg shifts about 1/8"

I have reconfigured a few things and shifted the CG up a full 1/2" on both planes - fortunately I was able to do this without adding weight.
I guess I will see how they fly and go from there.
DP