i have an 05trx 450r dune bike, not settup for drag but can hang with some.
ive beat many banshees, im not claiming that its fast but a banshee with pipes and pistons is not gonna catch me.
my bike does not have an hrc kit but has something like it... cam, piston,portwork, and untuned. it does not have a rev box.
if your banshee has work on it you should be able to beat my bike, maybe more compression.
on sand, tire selection and gearing is whats gonna do it.