In reply to peebles boy:
Red Cuillin would be alright once off the actual heather as they are quite rocky, but you'd have a lot of uphill pushing between the downs as they are pretty steep and unrelenting in places. The paths are okay from my memory.
Trotternish would be a far better bike in my opinion and have a mate that has done parts of it before. Still a few tough up hills but generally much more flow than the Red Cuillin.
Some of the descents out of the Cuillin Coires are also meant to be fantastic riding. And Glen Sligachan is one of the best days I've had on a bike in terms of surroundings, it's not all that technical bar a load of water bars but can't fault it for location. We stopped just before Blaven and came back the same way to avoid the big climb out from Camasunary and then the long ride round the road.