Most all aerobatic planes will stall with too much up elevator, it is rather normal. The farther back the CG the more prone to elevator induced stall as well as higher wing loading increases this condition.

On my 1/4 scale Extra I only had 9/16" elevator travel on low rates and it would do all the basic manuvers with that setting. I have seen new pilots with Extras and Caps pull full elevator only to have the plane snap over on it's back and head for the ground. Of course their reaction is to pull elevator to get it to come out and when it crashes they imediately blame a radio hit since they had no control. If you still have your plane you have probably figured out to neutralize the controls and add throttle (which is hard to do when it is heading for the ground) when the wing begins to fly you gently pull level.

Just reduce your low rates and the problem will probably go away. Also, do whatever you can to take weight off the plane, an ounce here and an ounce there will add up to a better flying plane.