Portable Aerox Oxygen options

Another question. I’m also looking for portable Aerox Oxygen units and wasn’t sure what would be a good size for two people that would fit nicely on the floor. I was thinking a 13CF and maybe a 22CF if it would fit without taking too much space. Feedback would be much appreciated.

The Aerox 22CF system doesn’t take much space on the floor, or will hang on the seat back in it’s optional carrying bag. The hanging arrangement works but I find it awkward to install.