Friend of mine and myself built a garden shed. Insulation is foam sheets inside. Then we got a used window AC unit mounted in the hole we made in the wall for it. We put a track across roof for roller hooks so can roll 1/4 size animals in.
Actually works good. Once below freezing we put a electric heater in it so meat does not freeze. Kind of red neck but it works.
I have a 4x8x8 cooler. I use a 12,000btu air conditioner with a second thermister wired in series to fool the air conditioner to stay on. I can get my cooler to -2 but usually set the a/c to maintain about 3 degrees. It works awesome.
you just remove the factory thermister, check the resistance at room temp, check the resistance on ice water, and find one with the same specs. Wire in series and enjoy a giant freezer.
I do not hang/age my wild game.
9 out of 10 times it is gut and skin where they drop.
The bigger the animal the more important to get hide off.
Moose can spoil in 6 hours with hide on the shoulders.
I also debone ASAP and put in cheese cloth bags.
I toss it in my little freezer at the farm overnight in separated layers to let air between.
Wrap late the next day.
Moose fits in 7.5cu' freezer easily.
Some times gets a bit crystally but cuts easier.
DO NOT LET IT FREEZE SOLID!!!!
It is not fun defrosting 40# bags.