I am good at building cars for enduros...
1) build it like a nitro. Every screw that goes into metal, loctite it. Every screw into a plastic part that doesn't need to come out, superglue it.
2) setup the car to handle neutral, not too pushy not too taily.
3) use rubber tyres... 1set of TakeOffs or Sorex will last 2 hrs. No chunking and diameter issues.
4) install a big bumper! make sure there's no space between bumber and the shell nose.
5) ShoeGoo the wing on before you screw it in
6) all wires must be tied down, leave nothing loose. Fix the aerial tube with a grubscrew if you can.
a) oil your 540 every battery pack change
b) have lots of chargers (4? 6?) and lots of batteries (10?)
c) practise changing battery without taking the shell off...