If you are using a leaky valve design, the O2 first stage needs to have a fixed, non depth compensated IP, but that IP also needs to be adjustable in order to fine tune the flow rate through the fixed orifice.
The first stage also needs to be well balanced so that the flow rate doesn't change significantly between full and near empty tank pressures.
The first stage also needs to be well balanced so that the flow rate doesn't change significantly between full and near empty tank pressures.