Too much elevator will cause a model to stall at any speed or attitude. What is happening is that the tail is generating enough lift (downforce) to move the wing to a high enough angle of attack that it will stall. The higher the wingloading, the more abrupt the stall will typically be. This type of stall is rarely symmetrical, so the aircraft will roll to one side or the other. The problem can be exacerbated by warps in the wing or tail.

I was at Morro Bay on Sunday... I had a very nice time there. I didn't see any models flying though.