This is my bosses trailer. I landscape for him but often I do odds and ends for him at his shop shuch as install air bags on his F-350, swap tracks and shocks on his race sleds (Turbo M-8, and M1000), maintain machinery and now lift his huge trailer with his step dad that if you asked me is 80 years old and crawls under trucks without a creeper with less thought put to it than I do.
We also added a hitch on the rear and some big casters in case of bottoming out. The purpose of the lift is to prevent the rear from bottoming out. We started by marking the location of all the spring hangers. Then we cut off the spring hangers from the frame with a torch and grinder. We cut all brake lines and any other lines that would be streached or in our way. Then we put 2 4"x2" square metal tubing with 2 2"x2" cross braces in between the frame and the spring hangers and welded it to the frame and then we welded the spring hangers back on.