Two of us riding 400's have same problem of tail bone ache. We found an air cushion at sporting goods store for $10-15 that works really well. They are the type that hunters use. Its one of those things with a valve that you open to let air in or out...really easy to adjust. Has a strap that goes under the seat. Sorta ugly, in camo colors, but it works well. I'm thinking of having a cloth cover made for it. Got it at a place called "Outdoor World" in Concord, N.C. I think its a chain store..not sure.