On TPIII when the frig was installed it had 8" of foam around it the box was 24"x24"x18 deep. It had a tapered top with 6"of foam and a very good seal.
In the center of the coils we would place 4 Vertical Ice trays, even in the heat of the summer in Baja we had Ice over night. Our system was air tight and it came on for 5 minutes every hour. You could set your watch by it. Used it for 7 years, no problems.
ole salts,smile
geneWj