Hey guys!!! I just answered a question similar to this a couple of days ago in another thread. Basically to prevent tip stalling you want the inboard section of the wing to stall before the tip. To do this you can do a few things...

1... Add a 4" long piece of triangular stock to the leading edge of the inboard sections. This creates the effect of sharpening the leading edge, inducing a stall in the inboard section...keeping the wings level.

2... You are correct in that drooping ailerons only work for some aircraft. It all depends on how it effects the angle of attack relative to the airflow. In some situations it effectivly increases the camber of the airfoil, giving you flap like characteristics, which is like reducing the stall speed of the section.... preventing the tip stall. If washout is built in it has a negative effect, because gross angle of attack is now too high in the wrong diection ( if that makes any sense ) in that it will just produce too much drag and have messy tenancies.

I dont like messing with the ailerons. It is far better and more effecting to add the triangular stock and modify the airfoil. It makes all the difference.