Hi all,
I think I read all post regarding a cave set-up and hence hope I am not being redundant ...
For two weeks now I have successfully been controlling the temperature of my 4.2 cu ft fridge by simply encasing the freezer compartment with polystyrene. The fridge is a pretty standard compact fridge from Frigidaire (this is the model:
http://salestores.com/frigid669.html) and uses the good old freezer tray with flap as its cooling coil. It obviously cannot be set to temperatures in the range of 50-55F, so what I did was slide a polystyrene sheet to serve as insulation underneath the freezer compartment and in front of the flap. I left small gaps, just enough that some cold air penetrates the now separate compartment. However, the key is that the freezer will stay considerably cooler switching off the thermostat before the bottom compartment reaches too cold a temperature. Once all is set and done you simply use the built in control to fine tune your desired temperature which to me appears adjustable in the range of 48-62F.
For humidity I have the vegetable bin filled with highly saturated salt water 9this also stabilizes the fridge's temperature fluctuation), and once the cheeses as in the fridge it seems that my humidity is somewhere around 85% (I would like to get this up a bit, but I am not sure yet how).
I hope this is some food for thought as a piece of polystyrene is just a couple of bucks and worth trying before you invest in a $70 temp control.