JetCat quite specifically wants the valve after the pump.

I, however, (based upon my limited model but considerable full scale jet experience) place the valve BEFORE the pump. It's my view that this will ensure that the fuel pump does not have an unlimited supply if it "runs away" as I've read can happen, AND that the flow AFTER the pump will also stop immediately (or almost so) because the pump will cavitate.

I might try an experiment to see if I'm correct.