If you want to go that route you can set it up as a switchable mix. A better route is to exercise the left thumb a bit and learn rudder work. Coordinating turns is the first rudder skill and a necessity on most scale and aerobatic planes, so you might as well go ahead and start working on it. The best option though would be to fix the adverse yaw by setting up differential ailerons. It's easy to do with your radio. Start with 1.5 times as much up as down. You'll find that it tames the plane down considerably.