I have a small 5 cf chest freezer w/ a ranco I use as a ferm chamber. For the last year I have been wanting to ferment 2 batches at the same time, but only 1 bucket would fit. So I built a box out of 3/4 in. plywood w/ some foam insulation sheets for the inside of the box to fit over the opening of the freezer...( thought of just making a collar but I needed 20 extra inches to fit the extra bucket and did not want to lift it over that every time)...The box has a handle so it can just be easily removed as needed to lift the buckets in / out. I had to build a shelf to go over the 1st bucket so I could put the second bucket on top of that.
The only problem I see with this is maybe the top bucket will be slightly warmer than the bottom one....just not sure how much...anyone have experience doing it this way? I thought of maybe putting a small computer fan in there to circulate the air, but not sure if that's necessary. If anyone has experience doing it this way....how did you control ferment temps? Did you just tape the probe to one bucket and assume the other would maintain the same temps?