Bill,
On my P/P-38, I started with the CG at 27%. Flew great but had a hard time getting off the ground. I slowly removed nose weight till I got the CG at 34%. It was still very steady in a loop. I added tail weight to try to locate the rear limit for the CG and flew at 38%. It still handled well at that point. Take-offs are good but could still use more power. Have not tested with a rear 9-5 prop. I hope to move the front engine (w/front wheel) back in increments of 1/2 inch to locate the rear limit of the CG but will have to do some calculation since I will be cutting off the fuselage end. What % is your estimate for the rear limit? You are right on the main gear. I have winglets on the wing tips and they look great. Not sure if they add performance. Very stable at a high AOA while flaring during a slow landing. Any experience with winglets?