Comfortable portable O2 bottle size in PA-28 (?)

[Canuck]

For those of you who carry portable oxygen in a Cherokee (especially the stretch editions like the Warrior and Archer), what bottle size have you found comfortable for slinging on the back of the pilot's seat without crowding back seat passengers? I'm looking at the 6, 9, and 13 cubic foot sizes especially:

http://www.aircraftspruce.ca/catalog/pspages/aeroxsys.php


Thanks, David

 

[Orest @ CYFD]

 

[BGFYankee]

 

[Orest @ CYFD]

 

[BGFYankee]

 

[arkvet]

 

[BGFYankee]

 

[Canuck]

 

[Orest @ CYFD]

 

[BGFYankee]