It definitely makes sense to store as much cold beer stuff in a keezer as possible --- even when it's not Earth Day!
I'm not quite sure how to best use the space of the beer tube. My thoughts would be to interlay bottles.. base to base, top to top. I think that would get the most. Perhaps...
For years, I've eyed the rarely used gaps between kegs in my keezer and thought "I should do something with that space." Sometimes I place a large beer bottle in the gap but for the most part, the space goes unused.
I typically use my compressor hump for storing beer bottles and the basket...