I would not do it - just too much weight back there. Also it would put allot of twisting forces on the bumper.
I installed a hitch on our previous fifth wheel (CrossRoads Cruiser fifth wheel) when it was past the warranty.
I decided to put a front hitch on our truck this time. May put a hitch on the rear of trailer in a few years if we don't like how the front hitch works out.
Take a look at this thread:
http://www.keystoneforums.com/forums...ad.php?t=27461