I have a molded fiberglass "tray" forward under the V-berth that holds 3 G27 batteries. I have AGM's there now, so 270AH +/-, they are each in plastic battery boxes, all held down by an aluminum strap anchored to the tray. Another G27 aft for Start. My boat currently bow light so I don't anticipate the added weight being an issue.

I think I will remove the molded tray and build a one new box that will hold two Rolls 225-250Ah batteries, so I'll be up to 450-500Ah for House. My Echo Charge will keep the House & Start safely separated. I'm thinking of building the box from 3/8" marine plywood, custom fit to the hull, glass the box in and paint, with a removable and fastenable lid.

Any suggestions on building a new box ?

thanks, cheers, John