Those little tiplets of yours are awfully far forward in the wing. Perhaps these are creating a de-stabilizing force that's competing with the vertical fin and rudder. My advice would be to rip them puppies off and see how the model flies without them.

Are they scale? I can't imagine them being shaped like that for full size. They don't look like the usual NASA winglets at all. For starters the ends of the ailerons are exposed. Certainly they would make lousy end plates for controlling tip vortices with then being so short at the rear. Perhaps this is what is causing the nasty tip stall, the vortix is sneaking around the ends of the ailerons and doesn't want to let go until you power out of the spin.

And I think what Will is reffering to is often called a dorsal fin or dorsal gusset. It's the short ridge running along the upper fuselage from the base of the more normal fin, ie: the bit they added when they went from the B model to the D model. Actually you've already got it.