Dave,

I prefer the Mountain High holster system. Set the flow in the range
you are flying, then you can use the pneumatic switch to turn the flow
on and off. It tends to save the over stress on the needle valve using
it as an on/off as well as flow control. The holster has straps so it
can be Velcroed to a side panel or around your leg. I very seldom
change mine in flight. Set it for the range of flight and use the
on/off valve if I get low.

Tim