There are racks made that attach to the rear ladder, if you have a rear ladder... As I recall, the bike then hangs vertically, which would allow you to tie it to the ladder at several points, giving more security and peace of mind. A 1.5" hitch with adapter is certainly a weak point for that much leverage and weight. You can also use that type hitch mount, but then attach a strap from each outside corner to an attachment point on the camper, relieving much of the weight and strain on the hitch connection. etrailer.com is a good resource for bike mounts, etc. Jay