For the front, I removed the tow loops and made a receiver type tube for each side. I used the original hardware to mount the new tubes. Two post will be better than one. I been making and using a front and rear bar to haul 20-24' steel tubing home for my projects. I never had a middle support and had to pad the top of the cab.
For a boat and 5er I would be using my air deflector mount for the rearward support. With my dual cab it will be just under 14' between mounts. I'll tie the two supports together.
I have thought of using a couple of 14' 2x4's for a
one man loader and then the 2x4's could be used to tie the front and rear supports together.