New guy needs a little help?

I am looking at building a Freshwater holding tank/cooler on my 17 montaunk. What I would like to do is remove the cooler and wood blocks in front of the console. Then build the water tank / cooler following the contour of the floor to bow kind. The basic design will be kind of U shaped /4 sided. The water tank 3 to 4 inch high then the cooler on top of that which would also be a seat and all of this would then attach to the console and be one big unit.

So I hope I haven't lost any one yet on what I want to do.
From spending countless hours on here reading about different composites building material, fiberglass and resin and what knot my head hurts.
Here is where I need help and or suggestions for strength and durability.

1) I was thinking of using a composite wood like coosa (if some body knows something better please let me know)
2)Using west system epoxy and using cloth for the whole build
3)using 2 inch polyurethane foam board for the cooler wraped with coosa and cloth.

I know I would also have to build baffles into the tank. So will this basic design work? Would I need to change anything? Also what would be the best way to secure this to the deck and console? Just make a putty from the epoxy with choped fiber and cabosil(sp) and use that to secure to console then use 4200 around the base of the tank and floor?

Thanks for the help
Jay

 

Is this for your personal use(drinking)?

http://www.epa.gov/ttnatw01/hlthef/epichlor.html

 

Hoty thanks for the reply no this is not for drinking. This would mainly be for washing the salt off of people and the boat.