Howdy!
You are right. The only hose that fits in that silly short tube is a 10' very thin (really cheap junk) hose.
We keep our hose (complete with end fittings) coiled in a 5 gallon plastic pail. With the lid snapped on securely, it makes for a nice mess-free storage container.
Over on the
R-Vision Owners Website there is an article by someone who mounted a storage tube under the bed with an access door in the outside wall. It looks really slick, and I am considering this mod for my rig.
I hope this helps.