I had about 6 planes when I change from a D7 to DSM9. I found the easiest process was to place the plane on a flat surface and using the old radio measure all the control surfaces with a ruler with respect to the flat surface and writing down the data. I measured neutral deflection, full up, full down, full left and right. Then I would set up the new radio and bind, then using a ruler and the data, adjust the trim accordingly. It was NOT perfect, but it did give a great starting point.