Neat ice box
My wife and I have used wire racks, plastic baskets with handles, and mesh bags that hung from hooks near the top, in various ice boxes. The best was the stackable plastic baskets with handles, which were available at Walmart, Target or Bed Bath adn Beyond, (my wife can't remember where.)The best part was this: afer all was loaded, I placed a double thick fitted piece of Reflextix insulating material (it's like plastic bubble wrap with two shiny sides)over the top of everything to keep the cold down below the cover. As the amount of ice, food and beverage goes down, the cover goes down with it, to keep the smallest space possible cooled by the ice. Use block ice, not cubes or chips if possible.In the case of the icebox having one side against the hull, I'd condider laminating two inches of closed cell foam against that side to add to the insulation. Any places too awkward for sheet foam installation to improve the original might be filled in with expanding foam product like Great STuff or it's clones. In Texas summer sailing (although it goes over 100, we don't sail if it's more than 95 F.)our ice box in the previous boat with only 2.5 inches of insulation, allowed 15 lbs of ice cubes to last four days with the above described baskets and cover. In the present boat we store groceries in the ice box and use a 12v Koolatron thermoelectric cooler for the cold stuff. Works well since it draws less than 4 amps when running and our solar panel will renew that to the house batteries even if we don't run the engine at least 60 minutes a day. It has an optional battery saver circuit to prevent running down the batteries.Hope this helps.