In my sidemount training, I was taught to have the long hose on the right tank and a bungeed second stage on the left. I clipped off the long hose regulator when using the left tank. The clip was attached to the right D-ring with a light duty zip tie. It is strong enough to keep it in place during normal use, but weak enough to break if you yank on it. You can get a large package of them for next to nothing, so you can do it in drills to your heart's content.A question to those who have a reason to breathe two tanks empty in eg. 500 PSI steps each (sidemount, maybe independent doubles) and dive with rec divers:
Do you rig breakaway boltsnaps (o-ring) or do you just tie the boltsnap and count on (when breathing out of the necklace reg) whoever may desperately trying to tug that (to them) "octo on a boltsnap" loose to go for the reg in your mouth eventually?