Shane, I think your bike is the same primary drive as mine as I was running 14/40 at Cadwell this year and was about 8500rpm at the end of the Park straight. Based on the gearing at Donnington I will probably start the first few sessions for the Friday at that then as I hopefully start to carry more corner speed I may drop the rear to 39. Ultimately your riding style, corner speed etc will determine the best gearing for you!