Here's an Idea.
Richard Kollman posted this on another thread
"Have you considered using 25 feet of ¼ inch OD refrigerant dehydrated copper tubing for an evaporator? I built these at one time clamped in back of a stainless steel
18 gauge sheet. I believe Frigoboat has this simple inexpensive type evaporator although it is wider than 8 inches. SeaFrost will make you an evaporator plate any size but it is not aluminum
roll bond. On more than one boat where evaporator coil was behind box liner and failed I clamped 25 to 35 feet of ¼ aluminum
tubing to box walls as a good solution."
Has anyone done this ?