Well, I made a big hole in the driver side wall of the camper. It wasn't without some educated guessing, finger crossing, breath holding, lots of measuring, pushing, prodding etc. but in the end it worked! Since I have previously stripped the exterior skin of other Four Wheel Campers, I was relatively confident in the location of the vertical and horizontal aluminum structure in side the walls and after about an hour of figuring I went for it.
Here is a picture of the 80's Fleet(same generation as my Blazer camper) that I completely tore down which gave me the best guess as to how much room there would be between the structure of the camper in the area I was hoping to install the shower.
Turns out the measurement was exactly the same! I like when companies follow standard procedure/sizing. After framing out the newly cut opening with some extra 1" aluminum square stock, the shower I bought had 1/4" of wiggle room between the propane cabinet and the next vertical support of the camper wall.
Not a window...
I had to trim the shower enclosure to fit up against the propane cabinet. I have since packed it with butyl tape so its water tight.
Currently the shower head is at 5'6" when in the holder. After the lift/tires it should be above 6' which is great because Im 6' tall.
Dry fit everything except the fill line.
Got some shims to tilt the tank towards the drain and some perforated metal strap to fasten down the tank.
Bolted down tank, hose clamped lines, replaced the fill inlet and ran new hose for the fill.
Finished all the hookups, ran a temporary switch to the pump and filled it with water to pressure test the system and then ran out of daylight. womp womp. I flipped the switch and my faucet was leaking so water got everywhere. The good news is the pump works, the faucet gets pressure, the shower head works, the fill/drain work and all seems well.