sounds like you need the bike carrier which grips the drop out on the front fork (with the whell removed - obviously). Thule make these and they don't need to grip the frame at all. Very stable, took my downhill MTB to the Alps using one last year.
Try The Roofbox Company, I think they're based in Sedbergh if I reember rightly, if not, they advertise in the back of Mountain Biking UK regularly.
Hyper Blue/Black Cooper. Side skirts/Aero grill, Milltek, chrome bitz and a scary roof graphic. A SKATEBOARD IS FOR LIFE NOT JUST FOR CHRISTMAS |