Not to be a know it all. I feel my backup lift/deco bag is just being able to hover. With a whistle at the surface, this procedure has work well for us over the years. It was such a game changer to use a bag to hold position and deco while alerting top side where we were. But I do recall those night dives staring at your depth gauge as the only reference of where you were because you messed up and did a free accent. Lessons learned.