rear bumper pulling away from frame

I have my bike rack supported from the back wall. I use 2 ratchet straps criss-crossed and a set bolt in the hitch to take out any slop in the hitch. I also installed 2 stainless eyebolts in the back wall, through the horizontal bunk studs and the vertical wall studs. I have had them (4 bikes) on some fairly long trips. the longest was to Macinac MI. installed properly it can be done! even just installing a standalone hitch to the frame is not enough. the bike rack needs to be supported to eliminate the bouncing that happens at the rear of a trailer.