Hey Windknot,
I think you may want to consider what rig you're using before deciding on the length of hose to order (at $30 a pop). For doubles, it seems like 22" would be fine (I'm not speaking from experience here). With a single tank, your tank is in the middle of your back vs. slightly to the right (the bungeed back-up would come off the right post in a double tank set-up). As a result, I think this may make the 22" a tad short. Tank position (how high/low you have your tank mounted) can also affect this.
I'm exclusively a single tank diver and tried the 22" and found it to be too short. I use a 26" now and feel it is long enough without too much floating in the breeze. When I ordered the second hose, I tried both on dry land while looking in a mirror to check how streamlined I am.
Hope this is helpful.
-LD