Actually, I think that energy savings in industrial refrigeration is a science. You can't measure real life capacity without measuring flow.
Rule of thumb. Keep capacity of screw compressors as maximum as possible and run reciprocated compressors as trimming ones. Efficiency of reciprocated compressor doesn't suffer as much as efficiency of screw compressor when it unloads.
Reduce minimum allowable condensing pressure as low as possible(winter operation). Keep optimum wet bulb approach for summer operation of the condensers.
I'm just curious. How did you determine that you have 3-5 psig of air in the system?