Take a look carefully at the pictures included in this thread...this or something similar is what it will take to strengthen the bumper enough for a hitch bike rack: http://www.jaycoowners.com/showthread.php?t=4448
I've used it for probably 400 miles so far and no signs of flex or fatigue yet. I'm confident it will last in this config. Definitely will post if I have any issues with it right away. The new appliance enamel on it should show "witness" marks if it starts to fatigue.