From my experiences a stiffer chassis carries more corner speed and transitions faster. A more flexible chassis digs a lot more in the corners and is slightly slower in the transitions. I feel that there is definately such thing as too stiff. A car set up like a brick tends to be harder to drive, and harder to make consitent. It makes it too twitchy. I have my 05 setup with the standard chassis but with the TECH upper deck, and I feel that the car is 100% better than stock, and it was REALLY good stock. I don't see any need for the Xenon chassis for carpet. I have at least 30 packs through my car on foams/carpet and it lacks nowhere. Save the money and get the TECH upper deck...or if you have to have the bling then get the Xenon, but don't expect to automatically go 3 laps faster.