Hang on, y'all. I CAN plug offboard into my loop.
What I was saying is that, to run offboard for my dil would mean (I think - unless I'm missing something here, which is ENTIRELY possible) having my BO bottle filled with dil and slung on my left side. That's where I carry it (when only carrying 1 BO bottle), and I have a bungee loop, so I carry it SM-style.
Using that as my one and only source of dil would mean adding a 2nd whip to that 1st stage (on the BO) and running one of those whips across my chest to connect to the Offboard plug-in on my MAV, running another whip up to the power inflator for my wing, and then, possibly having a third whip on it that runs to my drysuit inflator.
Once you move to something other than air dil/BO you will most likely have:
A suit gas bottle with its own reg and hose
An onboard dil bottle feeding your ADV, over your shoulder to your MAV, and your wing
A BC whip on your left BO that is tucked into the bottle bungies unless you need it, then it'd be removed and cross your chest to plug into your offboard MAV port.