Here's a shot that I liked from a few days ago. Tire slide across a small QP.
I set up a flash to the camera right and fired it at 1/4 power, wirelessly triggered.
1/15@ F/4.5. 28mm @ ISO 200. Moved the camera with the subject to keep him in focus and to blur the background. I could of had different camera settings, but I wanted to keep as much ambient light as I possibly could.
After submitting the image and reviewing the post, I notice that pinkbike has screwed with the image a bit. You can click it and things won't look as funky as they do on the forum.
Lookin' good dude. I think the comp is kinda boring, and it has to much head room...Also, I like your idea of wanting a good amount of ambient, but with this I think you could have speed it up a few stops. Very sharp and perfect focal point. Also, try this shot at a sunset time, a red-ish sky would look awsome here.