Hi AllI have to replace my ruptured (aluminum) holding tank and have already removed it from below the transom step (yuck!). I have read through all the earlier posts (I think), and didn't see an optimum. I am thinking of making in a custom-formed fiberglass tank (gelcoat on the INSIDE to seal it) below the stbd swim step. By making a plaster mold I think I can fit a 12 gal tank through the 10x14 swim step hatch without having to cut any of the transom glass. My questions are: are there any problems in using a fibreglass tank? Does anyone know of a better casting agent than plaster of paris (or paper mache)? Has anyone come up with a better solution that works (would Rick Dinon's approach be better)?Thanks for your help with this dirty job!Mike