If you have dual rates on your TX. try increasing the elevator rates on high by about 10% . Get your plane a few mistakes high and start pulling loops. If it doesn't snap stall to either side, the nest time you take her up set your low rates to the high rate level and ove the high rates up another 10%. step it up like that till you like it.
Remember, if your CG is close to its aft limit, when you hit the limit of elevator deflection the snap to one side or the other could be pretty violent.