Yeah, that's the basic and standard construction, and not my problems I am concerned about. The physical construction is easy. First is time. It took me more than 6 months to do what should have been a 2 week job on the floor repair, which still needs 2 trim pieces made, but I don't have the tools handy (buried in a shed at my fathers place). I have at best 1 day per week to work on the boat, and that is assuming I give up anything else I might want to do.(which I am really exhausted from and need a life back) I just don't have any personal time for anything with my current employment schedule. It just isn't sustainable, but it is what I have right now.
The other issue is the box size and shape. I am surprised Jim got 6cf out of it. I am trying to make it "usable" by squaring it up, so I can reach the bottom and so the bottom is flat and I can stack stuff well. I am coming up to about 3.5 cf total. 2.5 cf for a refrigerator section, and 1 cf for a freezer. That is a *lot* smaller than I want. The plan was to have two separate lids, not unlike the stock configuration, with the lid closest to the cabinet a 1 cf freezer, and the other a 2.5 cf fridge. Except that a 1 cf space won't quite fit where I need it too. My evaporator is 54" x 12". It will fold into a cube about 13.5"x13.5"x12" high. Front to back, the inside of my box will be about 14", so it _just_ fits that way. But I can't put it next to the cabinet, so it massively shrinks the fridge. That is why I was wondering about Jim's evaporator. Unfortunately, folded into a rectangle like his instead of a cube, It will still be almost 2x the size of his.
So yesterday I started looking at replacing the evaporator, only to discover that the kit I have, purchased used but still new-in-box, has an older connector style, and will not work with any currently available separate evaporators. I haven't decided what to do. I can by a new evaporator, then pay a tech to replace the connectors on my compressor, or buy a whole new kit.
The evaporator size I am looking at is 47.5" by 7.5" which will fold into 12x12x7.5. That I can tuck next to the cabinet, and will a slopped bottom from 7.5 inches to about 12 inches will give me about 0.8 cf. A bit smaller than I wanted, but workable. I would prefer the larger 54x12 evaporator for power to bring a warm fish to freezing faster, but it is just to big to fit.
I bought Nigel Calder's book, and using formula's in it an from other sources calculating what my expected Ah per day usage will be with various options. It's difficult to justify aerogel. Without aerogel and assuming being in the tropics, I am looking at less than 40Ah per day with 4 inches of foam. I will probably be less than that because I will have much more than 4" on the bottom. Aerogel could drop that to 35, or maybe 30, and I still would not be able to reduce the insulation thickness. I'm just not sure it is worth it. VIP panels are more tempting. With them I could drop it to close to 20Ah per day. But even then, 40Ah per day is pretty efficient, and much less than I was using running 2 chest boxes previously. (about 100Ah in the tropics) And for comparison, with the chest boxes, I has 2.5 cf of fridge, and 1.5 cf of freezer. It worked, but I definitely felt squeezed for space.