Got a lot of views, but no responses. So decided to step out there.
New filter cartridge. Set supply water pressure regulator to 50lbs. Observed toilet as flushed several times. Put a gallon container in galley sink. Timed fill. Moved container to shower. We are using Oxygenics. Timed fill.
Turned off city water and repeated above steps using on board pump.
Drilled the 5/32 holes in each end of the filter cartridge to 1/4.
Repeated above steps. Amazing! Increasing orifice diameter by 3/32 almost doubled flow rate using either city water or on board pump. Toilet and shower much improved.
. We boondock a lot. Going to use the large orifice cartridge when we have city water, change to unmodified cartridge when boondocking. Don't want to run through our water twice as fast.
Can't imagine how, but if this mod damages our system, will come back with update.