Safebet, I would also suggest the washout, even if I don't have it in mine. If I knew before I built it I whould build it with washout.

Also, just for you to know the theory, tip stalling is the opposite of what you described. The tip of the wing stalls first, and that is why it drops. That happens on takeoff because the middle section of the wing has air flowing around it from the prop, so even if the center of the wing has enough 'air speed' to fly, the tips don't. So if you take off too soon, one wind tip will drop because it is stalled. That is why most owners of this plane say that it ground loops immediately after takeoff.

Serafim