CS - I believe that the 32FX will rev higher than the 40FX making the plane even faster as the engine is lighter. You will have a problem with the 40, its about 4-5 oz heavier on the nose and this will not make it nice to fly as you might have to add weight to the tail. All that means higher wing loading. Why not try a 'dry fit' of the engine and see the balance. I think you are better off with the 32FX.