I have a 9" Ultimate in my car, it flashes around 4500 at launch and is ~5k minimum going down the track on nitrous passes. No issues with trans temp, the fluid always looks perfect and I've put thousands of miles on it, including a 700 mile drag and drive last month. I do use ATI synthetic type F though. It cruises fine with 2-3% slip at moderate freeway speeds. 30" tall tire and 4.10's. As long as you can live with the slightly disconnected feeling at low speeds I wouldn't worry at all.