I love to flat track, but am no pro by no means and can't tell you for sure, but the +4 axles have adjustable lenghts +2 or +4 you may even have one. What brand do you have? I have used the +4 axle and +2 arms and loved it, felt like it was on rails the corners were a blast. Maybe one of the true flattrackers will chime in and help you a little more, I dont want to guide you in the wrong direction, have fun with it!