We are avid bikers, too. I had frame separation and
fixed it. As an engineer, I have decided against a
bumper mounted rack. I think it would be too much for
the structure. BTW, the bumper is directly attached
to the frame. But, there's just not much to the
frame. The strength is in the skin, and the frame
pretty much just attaches the hitch and wheels.
Someone makes quick-release clamps that mount with
screws to any relatively flat surface. They're about
$20 each. They do require you to remove the front
wheel. You might consider these inside the trailer or
the bed of your PU (if you have one).
I haven't found a satisfactory solution, so I'm all
ears to someone who has. I don't like roof racks b/c
I have a full sized van. In addition, this location
isn't too "clean" on the east coast in summer time. I
guess you just have to chose your dirt--dust or dead
bugs :)
Jon in SC
1 1968 Overlander
7 bikes (and I haven't even started buying them for
the kids yet!)