I have a 26' Hunter and want to install a larger water tank for the galley sink. I was hoping to put it under the seat on the galley side. I bought something from West Marine but of course, I didn't measure and it doesn't fit - way too big.Has anyone found something suitable. I was hoping for at least a 25 gallon tank, although my boyfriend is griping that it will weigh down the boat too much.Any suggestions... Thanks,Mary