Forgive me if this was already stated... truthfully I didn't feel like reading all the posts, so I skimmed them.
To start I agree with what appears to be the majority of the posters. If you bungee your backup, you will find air sharing more comfortable with a longer hose, at least equal in length to a standard octopus hose.
That being said, I don't see why you couldn't use a standard primary hose. In regards to air sharing you would be under the same close quarter restrictions as using and AIR 2 type device, without some of the other restrictions of the AIR 2 type device.
Like I said, I believe most people would find this limiting to say the very least but it is doable. Anything can work - albeit some solutions better than others - if you work with enough to become comfortable.