My diving partner, at 20 dives under her belt, was a bit apprehensive when I told her that I’d like to change my configuration to a backup on a necklace and plan on donating my primary. Her concern (rightfully justified) was that in an OOA situation she had been trained (as most of us have) to go for the backup, almost always found at the end of a bright yellow hose. So as an intermediate step, I bought a bright yellow 40” Miflex hose and secured it to my primary (as noted above, an angled adapter makes this pretty comfortable). After practicing OOA drills almost every time we go out, I think we’re almost ready to use a long hose….note, if only they came in yellow I would have started with that route!
Interesting situation. Good food for thought:
1. When I show divers how to take their 'standard', or at least already available, hoses and configure them for primary donate, very often the 40" hose that becomes the primary is a yellow hose. While that 40" works in an OOA situation, some divers want a longer primary for air-sharing - 5ft, 7ft., etc. AND, you can actually order a custom
yellow hose in a variety of lengths (
Low Pressure Rubber Regulator Hose - Regulator Hoses - Scuba Equipment Dive Gear Best Prices) - including 5ft and 7ft - to use as the primary, and which also serve as that yellow 'beacon' to OOA divers.
2. A number of divers (myself, included) who dive in a 'primary donate' configuration use either a yellow purge cover on their primary, or get a yellow case for it, to address the very issue that you raise - many divers are trained to look for yellow. Purge covers are easy to swap, at least on identical second stages.
3. In reality, if divers are in good horizontal trim to begin with, and an OOA / LOA diver approaches their buddy, chances are all they can really see is the second stage in their buddy's mouth - i.e. the second stage that they are going to get when air is shared. While it is great for us to tell divers to look for the buddy's alternate second stage in 'the triangle' (I sometimes tell students that it may as well be called the 'Bermuda Triangle'), in many cases that is not readily visible. What IS immediately visible is that second stage in the diver's mouth.
4. I do not know from your post if your dive buddy has experienced diving as the OOA / recipient diver, breathing from a second stage on a long hose (7ft), that you are supplying. If not, once she tries it, I suspect she will love it. It is SO-O-O easy. My wife and I both dive a long primary hose. And, her SAC is lower than mine. So, when we dive on Bonaire, we usually spend time a) practicing air share drills, and b) using an air share - from her to me - to balance the gas supply in our AL80s. With a long hose we can swim comfortably, near each other but still with a bit of separation, along the reef and see the cool stuff, and end up surfacing with the same amount of residual gas.