[Tempted]

You won't really lose any punch but you will stress the motor a little more causing some heat. If your going to be running in mains, you need to keep the temps down as much as possible. 45mph is very fast on a track and at 55 you would need to start braking much sooner. This could cause some control issues entering the turns and probably equate to slower lap times. You best bet is going to be gear for 45 and drive the track a few times. If you feel you need more speed, gear up a little until you find the perfect set-up for your driving style. Everyone runs different lines so your times will vary from others running the same gearing. Just find what suites you and win some races.