Where do you put the sewer hoses? I made a plate 1/4" to mount on top of the existing bumper. With the 2" bike hook up welded to it plus the tire mount. This gives tha bumper added support and NO twisting. My sewer hoses are secured in with 1/8" tent hooks. I drilled holes through the bumper and the rubber block, The 1/8" tent hook keeps the blocks in.
I did a similar deal as you did on another trailer. But extended it 18" to hold a tool box and my batteries.
Cheers all
BUT a very nice job!!:B