Bike rack results ---help!!!

Well we tried the 2 inch receiver on the back bumper bike rack option with a 4 bike rack. Was working great until we found out it was actually pulling the bumper off of the trailer. The welds of the bumper are now pulled open. Guess the bike weight was too much. Question: Has anyone ever attached an actual receiver hitch to the trailer like on a car where it is bolted to something solid? I think this is my next option since the bumper idea won't work for our heavy bikes. Also any ideas on how to fix the bumper?