I have a bunch of rc cars too and always wonder how i could use the radio and servos to make a cool prop, but I never get around to doing anything with them. Would love it if someone could toss out a few ideas to get me rolling.
I think your limitation with a groundbreaker is that they're typically only half a body and such a body realistically wouldn't be doing much gliding Having said that, what would help the illusion would be to have that half body positioned horizontally on the RC car and have tattered shroudlike material dragging behind as it moves. If you could find a way to rig it so the arms moved (as in dragging itself along), that would be even better.
Another possibility is to put something like a spider on the RC car. A remote controlled arachnid chasing ToTs would be a very effective addition to a haunt if it fits your theme.