If you're looking to help avoid tip stalling then look into the idea of ending the ailerons well before the tip. Having a segment of wing with no aileron that is about 1/2 to 3/4 of the tip chord is often seen and is used normally to help avoid increased tip turbulence. But decreased tip turbulence goes with a lesser chance of a tip stall. I've got nothing else to base this theory on but perhaps some others can comment.

Often a hack ship modifed to test such things can tell you a lot.