high volume needs with driven point well

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Trying to determine how to design a system that will handle a custom shower with a maximum flow rate of 20gpm.

facts:
1" IPS hdpe from the well to the jet pump delivering 12gpm at present
gould aquaboost II pressure booster pump down line from the jet pump
19 gallon horizontal pressure tank supporting the jet pump

unknown:
well yield
well capacity

I was considering installing atmospheric pressure tank(s) to boost available water.

help please.....