Maybe it is just me but I avoid drilling the sides of the camper, especially when there is an easy alternative. For an outdoor shower stall I open the rear door 90 degrees. I clip one end of a tarp to one jack bracket, clip the middle of the tarp to the top corner of the door, and clip the other end of the tarp to the other jack bracket, creating a triangle shaped space. I have a couple of strings attached to the bottom grommets of the tarp to hold it outward if needed. Everything, including a silicon rubber pad to stand on, fits inside the propane hatch. Yeah, tarps look third-world, but the thing is only up for like ten minutes then it disappears. I hang a Stearns 5 gal solar shower bag on the top/back of the camper (installed a hook). For cold weather I have an indoor shower setup as others have done.
In my experience, everything bolted on the exterior gets destroyed by wind, UV, air pollution, and tree branches.