Wes:

As the only things that are really affected by the forces in a spin are the clunk and the fuel in the tank, I think your next check is to see if the engine is more liable to cut if the spin is done with a low fuel level, or if it is equally likely to cut with a full tank.

My thought is the line on the clunk - it might be just that little bit too stiff and it doesn't stay in the fuel when the spin is throwing the fuel around.

So put the most flexible hose you can find on the clunk and try again.

Bill.