I thought it was weather helm that caused the loss as I've experienced that before on the Beneateu as said but in reading you post again it seems that when the boat is being pushed upwind and rolls over the rudder comes out of the water so much that you loose control due to cavitation from sucking air or simply not enough surface area. Never a good thing.

I'll still stick with just reefing to bring the boat more upright putting more rudder in the water and call it fixed. You chose the vessel for it's draft and that's the trade off. We chose ours as a condo that sails and it does it's purpose well but, you'll pass us every time.

An Ovni has double rudders to solve your problem as one is always fully in the water.