This is where design could be beneficial. The size and position of the ailerons can give them a more consistent response through the speed range. Look at some Q-500 pylon racers. The barn door aileron set mid span but with a wider chord allows you to almost eliminate the use of dual rates. Full span strip ailerons could be the issue here. Honestly with a plane like this, You will just have to get the throws down and live with it, if you do not have expo. The other aileron configurations should be considered on the next project maybe.