*IF* you can get very close to the track, like the Audiclub tent at Laguna Seca turn 5 where you are maybe 10-20 yards away, a 200mm on a cropped body is more than long enough. I was shooting more at 70mm than at 300mm on my D200.

Since Rice Etr will be at Thunderhill, for shots down the straights, coming out of turn 12, etc. a 200mm should be adequate. If he also wants shots out of turn 5, 9, etc., he's gonna have to get permission to walk out there, which may be possible at a DE, or else then he will need a long long lens, like 400mm.

BTW, if he's talking about the Audi DE in January, I should see you there, but be prepared for rain and cold!