I used the suction mount the gopro comes with and no height extensions. The suction cup is mounted to the side of my helmet, you can sometimes see it in my rear view in that video IIRC. Skeleton case for more engine/tire sound, there is actually not much wind flow in the E92 with the windows down compared to most cars.
Unfortunately the thing won't mount on my helmet now because I had it mounted where my Hans anchors now are. I may remove them now that I don't have a car with a cage/harness setup to use a Hans with anyway.