You can see in this step how I notched each rafter to fit more securely to the walls. I also used a metal hurricane strap to secure each rafter to the wall. Even though this was not required by code, I felt my tools were far to valuable to be left to chance over such an inexpensive solution. The walls are a simple board and batten system. The 1x3 trim covers the joints of the 4x8 OSB. They make much more high quality sheets goods to use as siding. However, the cheapest I found was $35 a sheet and the OSB was about $5 a sheet. I sealed the OSB and painted it with exterior paint. If I run into problems in the future, I can just add a second layer of more durable material or simply have siding installed. It has held up very well over the past couple years and I see no need to spend more money on it now.
The refrigeration setup in your van is an area where you really do get what you pay for, whether you’re paying in money or in time. The best options are the most expensive. The cheapest options are a pain and/or don’t work very well. And if you try to save money with a DIY refrigerator setup, you could end up spending a lot of time on installation.