He races the BBORR also, runs the unlimited every year I have been there, he also has left the road once at silver state. He added diffusers to the back and said it helped a lot.
I had Roy's Mk1 GTD40 up to just over 183mph a couple of months back and was kind of surprised just how stable it was at speed. Just wish we'd had a video running at the speed trap now cos I suspect it sounded better on the outside than in. Given room I reckon it would easily have been into the 190s or maybe even reach the magic 200.