Two sets of PEX supports complete, with banana for scale.

I've already put the top support on the wall. For the center section, I found a stud to put some screws into. The left and right pieces were more tricky. I needed to make a wedge shaped piece of wood that could be screwed to the wall at just the right position to match the sloped plywood. To accomplish this, I put a ball of plumbers putty close to where I thought the support would be, then smooshed it against the wall to make the wedge shape that the wood needed to be.