The walls are closed now, after passing the water pressure test. I installed cut off valves in the underpass, where they would be more useful. My toilet, washer machine, and MB sink, were all on the same water line. So if one of those failed, I would lose the use of the other two. I am thinking I will never sell this rig, now that I have heard the marketing and experienced the actual. If I ever roll this rig, I am thinking the shower, may be the only section to survive the wreck...LOL!!
The next step is to seal the seams and screws with tubes of silicone. On a side note....working with "Go Board" was way easier than going the traditional cement backer boards. However, the boards are not to be trusted for screwing in items like a fan control or light switch. I ripped in and floated a piece of wood at that area, so the screws had something to bite.
Here is an installation video, showing how to work with this system. I contacted them about installing this system in a 5th wheel and they said it is fine. It is rated to -20F. The sheets come with a protective wrap on them, so making cut marks on them is not a problem.