It seems to me that wing rock is generally a stall on the tips. If that is the case then cutting the tips off will improve it because it will add a thicker wing at the tip. I would also assume that Tip stalling plates will also help some degree.

Why would spoilerons work? It seems they create more wing area and a nose down moment. Also The Mini 3D looks like it has about the same design as the UCD wing, why is the mini 3d able to do harriers better?