JudyMusic, Your TT square tube bumper isn't designed to carry any load, mine is rated at 70#, not really enough for two bicycles. You need to find a good welder/hitch shop and see if they can come up with something to extend your trailer frame and make a custom rack. Remember that the more weight you put on the rear of the trailer, the less weight you have on the tongue, you want to keep about 10% of the trailer weight as tongue weight or your trailer will sway badly. Be careful and find a good hitch shop to help you out.
Bill, Kathi and Zorro; '05 Beaver Patriot Thunder
2012 Sunnybrook Harmony 21FBS (SQEZINN)
2007 Jeep Grand Cherokee Overland