Just an idea...
I know a fridge or freezer is more efficient when it's full (more thermal mass). I've heard of people filling a partially full freezer with Styrofoam to make it more efficient. This gave me an idea.
I'm building a 4-corny keezer, and was pondering making a foam insert for it. The insert would basically fill the whole keezer, with a hole to hold each corny, and another for the CO2 bottle.
I think that in addition to helping the keezer be more efficient, I'm thinking this would also help reduce stratification. I know I could accomplish this by using a fan inside the keezer, but sometimes I like taking a different approach.