Just trying to be helpful. Some jump to such planes with less experiance. You could try a uniflow tank. That would be more tolerant of high angle of attach + increased muffler pressure. With a pusher configuration a simple tounge muffler should work. Or cap the exhaust cut a hole in the side and route a new stinger out the side and toward the back of the cheap Tower muffler. That way you can get that possibility off the map and keep oil of the plane at the same time.