Has anyone made Polar Tubes before?

since cold air sinks, i bet there'd be value in fastening several of these together to completely cover whatever's in the cooler.

Craig, the beauty of the sponges are that you can stuff one in the gut cavity as well.  They stack nicely in the freezer above the compressor in my chest freezer. 

My kill bag is flat bottomed, but tips forward towards the back of my kayak seat while on the water due to the shape of the Revo tank well. Frozen bottles just rolled to the lowest point and the fish would slip to the back and not be on ice.  The bricks lay flat so the fish sit on top of them much more effectively. 

The Polar Tubes could easily be made to fit any kill bag lengthwise to eliminate unnecessary bunching up. 

Good idea!  I was wondering what I was going to do with all the pvc and I had leftover from an old kayak shed I made a few years ago.