Garth,
I had severe seperation (I could see the 3/4" plywood in the gap). A suggestion I got from a man who restores old railroad cars worked great. I took off the cover to the storage box in the bumper and removed the rivets in the decorative band that goes around the trailer just above the bumper. and bent them out so I could get to the skin of the trailer. Before this I had the rear bumper on jacks holding up the weight of the trailer to get everything back as close as possiple to original position. I took a 2" L aluminum channel and had to cut down one side to 1 1/4' (metal cutting blade on table saw) You then rivet the bottom of the ell to the bumper and the verticle side to the trailer (hopefully getting rivets into the floor channel)simple cuts in the bottom of the ell will allow it to curve around the ends. Bend the decorative band back into place and rivet it to cover the patch.
If you have questions, email :
www.stagecoachbill@msn.com