I run the small tube and I like it. I know a guy that runs 425 and won the track championship on a low bite surface running the small tube. I don't know anybody that has been able to make the std tube run unless they are very good with tires. Unless you run really high bite stuff I'd run the small tube. As dirt Karter said....JT sucks with customer service. It's one reason why his best drivers running his stuff have left him. I'm waiting on a phone call back from him from 8 mths ago and called 3x to buy another chassis from him for a buddy and can't get a call back. So take that for what its worth to you. If you have guys you run with that run that chassis and you can help each other then get on one. If you need/want factory help from Millenium, I'd consider another mfr.