My recommendation is to switch to doubles. BUT, I used a 40 for a few years on a bracket, and that is really not a great way to go. Much easier to sling it under your LEFT arm. I pressurize the reg before entering the water, then turn the valve OFF, to prevent free flows. the major issue with the bracket is needing a longer SPG hose and mounting it so you can access the valve.
i do the same only difference valve is always on. Why are you expecting a free flow ? Most of the reg now have a pre dive, dive switch.My recommendation is to switch to doubles. BUT, I used a 40 for a few years on a bracket, and that is really not a great way to go. Much easier to sling it under your LEFT arm. I pressurize the reg before entering the water, then turn the valve OFF, to prevent free flows. the major issue with the bracket is needing a longer SPG hose and mounting it so you can access the valve.