Ignoramus31823 fired this volley in
:

If the "loss" that occurs during initial pumping up is small, then the
tank is slow to fill, and it means that it will not be filled fast
when the system reaches pressure.

So? You said you only need it for occasional "high flow" jobs. If you
need it to fill faster, install a manual valve to override the restrictor
when you absolutely have to, and let the pump work longer in one session.
(the total pump time will _always_ be the same per cubic foot of tank
capacity, so you save nothing in pump run time, either way. It either
runs in 'bursts' until it's filled the big tank, or it runs
continuously...total time is the same).

Again... remember that you're only drawing from that big tank when the
small one can't provide the flow you need.

LLoyd