Sanding upside down is probably the worst job on the build. I had to sand the joins on the cabin side to decks this week when I prepared them for taping. Below is a picture of the join before I taped it. I was really happy with how neat these joins ended up being.
Now that I have competed taping on all of the cabin sides inside and out and patched the areas that I needed to sand back off where the glass did not adhere properly, all that is left to do is close in the rear cabins (port is the bathroom, starboard is the rear bedroom). These will probably need to be strip planked or kerfed as the side deck profile curves down toward the rear steps and I need to match that curve, and over such a short distance it is probable that only kerfing will allow me to get the curve right.