I could be wrong, but is the dip tubes smaller in diameter than a single, all mine are single. I use them for 100% o2 hanging under boat with two regs, as a safety precaution on deep deco dives.
What is your purpose, your redundant air source, If so the H valve was the way to go back in the day, and in Europe.
I guess from your area, witch I was Great Lakes, the reason was reg freeze up, yet it never involved the valve. I do like the Idea, just it is extreme unless Ice diving in 40 below. To date my double hose and any old valve I could Ice dive The Great Lakes, any time of the year.
I do like the set up though of dual dips.
Happy Diving