If the tip stall you are experancing is in the form of an aleron reversal how dose the airplane respond to the rudder. Tip stall is coused by leading and laging wing. With a swept wing as a wing leads it appears to the air to be longer and provides more lift and as it lags it apears to be shorter and provides less lift. There is a condition kown as adverse yaw when you deflect an aleron doun you increse drag and couse the wing to lag and you can actuly have less lift. The cure if you are not good enouph with your left thum might be to cuple the rudder and alerons so they work to gether If you have a computer radio you might program it to a rate switch so you can turn the cupling on and off. I think the C.G has little to do with your problem. Joe