Give your pilot a break. Start flight testing and trimming using a 7x6 or 8x5 and run it fat! Work up to the full-race configuration. A slightly untrimmed B-TR (and critically--the landing gear trim, too) will eat the pilot's lunch and do severe damage on a takeoff accident. Getting a B-TR trimmed and set up right is harder than most other planes in my experience. Some never are right due to design features that sounded good and looked right (based on general practices, sport planes, stunt planes, etc.) but will not work on a B-TR. I have helped flight test four different planes. Two of them never were capable of being raced. My two cents...
McSlow