This really isn't a valid example. It's impossible for such a model to fly straight ahead with all it's wing on one side.

Actually it would still respond with a side slip as with the lift centered on the horizontal panel and the weight very close to the fuselage the fuselage would immediatley begin to drop bringing the rest of the wing with it which would give you a side slip condition in any event........

FWIW, I too subscribed to the "classic" dihedral explanation for many, many years. But if you look at it in real life there is just no way for the unequal projected length factor (which I admit is still valid IF it could operate in isolation) to be the dominating condition for more than a few milliseconds just at the completion of the roll in action until the model accelerates into a side slip condition.

This is fun...... Can we debate the temperature of inter gallactic space next?????