I've got a tire mounted on the rear bumber of my
trailer (1960 tradewind) and I can't imagine my bike
would even come close to that weight - although I
don't think my bike weighs more than 15 pounds...
wouldn't it make sense to attach them to the tow
vehicle?
here's a thought, though I don't know how legal it is:
I've heard of having a hitch receiver installed on
the front of your vehicle (handy for parking a trailer
in a tight spot) why couldn't you attach a
receiver-style bike rack to the front and put your
bikes there?
It would be silly if you were trying to haul more than
just a couple bikes, but it's a thought!
Toby