-use "locktite" on all the screws so the car doesnt fall apart during the 45 minutes!
especially the motor mounting ones.
-get a cordless drill, with the proper bits for the nut, and change wheels like nascar really fast! lol
-gear it down , as everyone has said
-reduce the dual rates, so you dont scrub off speed through the turns, and for a better line.
-get some of those 2000 mah nimh AA batteries to put in your transmitter, not those cheep 700 mah nicad sanyo's. charge them before the event.
i thought the lower the charge rate, the longer it would go? well, if i were you i would charge so the batts go for endurance rather than speed. if you have lipo batteries, use them if you can!
though, i wouldnt be suprised if they arent allowed.
i wish there were an event like that at my lhs, sounds like fun.