Another thing, look closely at your linkages. Make sure nothing is over extended or binding. On high rates there should not be a pushrod hitting anything or a connnection at the servo arm or control horn that is in a bind, misaligned or putting pressure on the linkages. The pushrods should not bend or flex at any point in the range of travel.
Everything should remain free and unbinded if all is setup correctly. Go very carefully when making these sorts of changes as overdoing it could damage the linkages, and make the plane difficult if not impossible to control.

Im concerned, I dont want you to overdo it and crash your plane or get yourself or someone else hurt.

J