I'm in the process of a complete overhaul to my 13' Scamp. Many upgrades, not the least of which is an outdoor shower.
When at most RV parks, it occurred to me that the curbside/entry-side is most "private" side, so I located my shower there, just below my "porch" light
. This location is on outside of the vertical cabinet inside, so the plumbing is hidden within the cabinet. I'm customizing the interior of the vertical cabinet so that I can have access to all the plumbing, while adding more efficient storage.
Obviously, the shower required cutting a hole into the shell. No big deal, IF you take MUCH care with your measuring and your cutting. I had no serious problems and the results are great.