We talked about this before. I was baffled then, and I am baffled now.Rather than start a new thread, I figured I'd ask here because it seems related to a BP&W discussion and the initial question has been answered. So I hope this isn't considered a thread highjack.
I dive a BP&W 95% of the time with a single tank and this issue did not occur when I dove doubles. I keep my backup reg on a necklace around my neck. Whenever I place the tank a bit lower so as to reduce the amount the valve of the tank is directly behind my head, the hose for my backup seems to get caught/hung up on my wing. When I have the backup reg in my mouth, this prevents me from being able to turn my head left much unless I reach back with my right hand and slide the hose up a bit.
Is this just the reality of a BP&W rig and diving with the tank valve directly behind my head is the best/only option? Having the valve that high is uncomfortable and seems unnecessary when using a single tank. Might it have something to do with using an STA? For example, if I did not use an STA and the tank sat closer to my BP&W perhaps the hose would not get caught up?
Obviously, I could put in some pool time and experiment with configurations, but getting a head start on ideas would be nice before doing that. Thx.
I, too, switch regularly between doubles and singles. I, too, use a STA to make the switch easier. I have enough regulators to have a single tank setup and doubles setup, so I don't have to switch hoses, but my alternate hose for my single tank setup is the same length as the one for my doubles. Since it does not have as far to go, it is actually a little too long in the single tank setup. I have never had the problem you describe.
From what you describe here, it almost sounds like your alternate hose is too long.