I have a problem...

My 72" Edge 540 has a tendancy to drop a wing and go into a spin when you pull on high G's.

I have balanced the model and it flys ok doing big manouvers, but if you fly too slow or pull on the G's it will snap dropping its right wing.

I checked the lateral balance and had add a bit of tip weight to the left wing, but still there is no real improvement..

Is there anything else I can do to stop this from happaning?
I am putting it down to a poorly designed model.

Cheers