And it looks like...


Next, in my mind, the area I was attaching to need a bit of reinforcement.. so I cut some 1/2 high quality plywood strips and secured them in place with clamps and a little silicone..

Then it was time to apply a good bead of silicone to the mounting flange of the shower box..

I then placed it in the hole, and secured it with 2" stainless #8 screws. They go through the box, the trailer and the 1/2 backing I applied around the hole..


I then ran a bead of clear silicone around the outside of the shower box to seal it.

The one and only caution I can think of is to check from the inside, the location of any wiring or gas lines etc. On our 177 there is a gas line that runs very near where I made the cut, but was clear of where I was cutting, yours may be different. (you can see it in the 3rd picture, a black line running in the lower corner)
So that's the outside, plumbing is next. I am doing it with PEX, but there are a few different ways to do it, but I have the tools, and PEX is what the factory used..