Fuel Tank Access and Decking

[woodman7975]

I have a 1988 Sea Ray Seville 18' that I am restoring and I have finally gotten to where I am ready to put the fuel tank back in and start the decking. The fuel compartment is approx. 54" x 30" and sits between the driver and passenger seats. The decking originally had a piece of plywood big enough to cover the compartment and you could remove it with screws and access the full gas tank. It had cleats (1x2s) built to the inside on the stringer and screwed to the stringer and the panel was screwed to these cleats. When I pulled the tank the area around the access was pretty badly rotted, so water had been getting in there from above at some point. I just bought the boat last year, so I can't speak to what happened before, but I do plan on having the kids in and out of the water either tubing or swimming a lot so there is a lot of potential for water to get in. I like the idea of having access to the complete gas tank, but I do not like the idea of how much water it could potentially let in. If I decked over the top of this and glassed everything in it would be for the most part water proof, but then you would obviously lose access to the tank. I do plan on putting in a circular access hatch so that I can access the fuel lines and fuel pump if needed. What are the opinions on decking over this area vs putting the access panel back in again? Also, the fuel tank compartment does not have anyway to get water out of it. Would it be a good idea to add some holes for drainage at the back into the bilge?