ffde asked about a pony, not a deco bottle. On a stage, I use a small face spg on a 6 inch hose. On my O2 bottles, I have a button gauge. On my pony, I check the pressure with a gauge prior to hooking up the 1st stage. I then pressurize the reg and shut the air off. Even with a pre-dive/dive switch, there is a small free flow risk. If you have an OOA event, it doesn't take much to turn the air on. BTW, I sling my extra tanks.