V-berth; installing the water tank

The aft partition was made of 1/2" plywood and was glassed into place using two layers of biaxial cloth.
We ordered a 30 gallon water tank to fit the space under the forward berth. Once the tank arrived and we made sure it would fit, we glassed in the forward partition. The tank was placed in the space and two part expanding foam was poured underneath the tank. We did the pour in two stages; during the first stage the boat was a little cooler than the recommended temperatures for the product and it did not expand as much as we expected. During the second pour the vessel was warmer than the recommended temperature and boy did the foam expand!
The stuff is very temperature sensitive to work with. Once it cured we used a large serrated bread knife to trim it; the large serrated blade goes through the foam very easily. The foam was shaped using a 4" grinder with a Zirconia flap sanding disk in it. After a few minutes the grinder quit working and I switched to my spare; I'm used to burning up grinders as the fiberglass dust is very hard on them and always have two on hand. After a few minutes the spare quit working. I think the foam dust was melting on the armature and fouling the brushes,......I'll have to disassemble them when we have time and see what happened. I switched to an air powered die grinder with a 2" sanding disk and finished shaping the foam. The foam was then resin coated with west system epoxy. Once the epoxy cured it was sanded and painted with Pettit Dura White paint. They claim mold and mildew will not grow on the painted surface so we are using the product throughout the cabin and lockers. The forward partition has three 4" holes in it; two that allow ventilation to the compartments outboard of the water tank and one in the center to access the tank vent fitting. The aft partition has two 4" ventilation holes outboard of the water tank that will have covers that can be screwed into place if desired. It also has two holes in the center to facilitate the tank filler and supply line fittings.