Ted, that might happened for that particular race at Charlotte, but in general most European chassis are set 50/50 and rarely touched. They more play with other elements like tyre pressure. I have tested for several manufacturers there and they rarely play with cross, and on those years they didn't even use scales. Once the seat was set the tuning tool other than the front end would be torsion bars, seat struts, axles and hubs, etc. A reason why they would leave the chassis at tracks after big races was that those frames were very fast but especially built for those top drivers and flexed a lot after a single race, so useless for their purpose after that, and besides it was very expensive to fly back with all those frames back to their shops in tdifferent countries, especially when coming to the US or even when they travelled from other countries to race for example in Italy, where most sprint big kart racing took place.