The 6.5 is perfect for me. I don't crave insane speed just a ton of torque so this is a perfect setup. I usually get 40 to 45 minute run times on my setup and the temp never goes over 130 degrees. Geared at 70/13 and I have a front and rear cutout on the body for good airflow.

One last thing, the brakes are insane on the 6.5, I had to turn the EPA to 85% to keep it from flipping on its lid!