We did use normal cos11's, we had 6 or so GoPro inside the cabin which we initially thought to plug straight into, then realised they wouldn't power the condensors, in the end it was a bit of over engineering to get what we wanted but we used the 302/744T with a couple of lectros gaffed really securely in the boot.
The reason I didn't mic the contestants helmuts was purely because we had them taken off after each run.
That said, try it if you can because it does get stupidly loud in there.