Lipo batteries are absolutely fine to fly with. They must be hand carried and not in hold baggage. Tape the terminals and put them in a lipo charging sack and be prepared to let the TSA inspect them when you go though the security scanners etc. Its much easier than you think to travel with your RC kit.
Just remember that as above you can't take fuel, additive, motor spray etc and all that can be sourced at the destination. I'd recommend hand carrying your car, transmitter and lipos and put the rest as check-in baggage. Should the worst happen and your check-in baggage does get lost then you'd still be able to race with just your car, transmitter and lipos! Us RC folk are pretty helpful and I'm sure you'd be able to borrow the stuff that the airline had misplaced temporarily....
I wouldn't worry about a pit-person... Ive always managed to find another driver/driver's pit person to help me out at the bigger races where my usual suspect can't come.
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