Freezer fermentation temp control without collar

So when I built my fermentation chamber recently I really wasn't thinking about 10 gallon batches since I don't do them often.

I can fit two carboys in the freezer but only by setting one up on the hump, when I do that then bout 2" of the neck of the carboy sticks out.

Current plan is to get the carboys at the same level (so put a milk crate in the bottom of the freezer) and then just temp control the air of the freezer to about 4 degrees below temp and throw a blanket over the top as a temporary lid. I don't want to take the time right now to make a collar for it.

Can you fit a bucket on the hump instead?

Hmmm maybe, I'd need to find a 6 gallon or so bucket and lid somewhere though. Are you thinking that the freezer would have to work too hard with the lid open/only covered by a blanket?

You need the moisture barrier of an air tight seal otherwise I think it'll frost up bad.