I'm certainly not going to suggest DP would have any success in NASCAR, but I don't think that it being too "physical" is what would hurt her chances. Ever watch the in-car cams on the IRL road courses? You can't tell me that's less physical than what the NASCAR drivers are doing, and it's at much higher g-forces. The reasons why she would not do well in NASCAR are too numerous to mention here, but the physicality of the driving, or her fitness, are IMO not a factor.