Reservoir and limit stop valve

The springs for the limit stop valve are leaf contacts salvaged from a discarded electric kettle.   These seemed a perfect solution after grinding off the contacts, soldering them to a small brass strip and mounting on a wood block. No indication of pressure on the valve is given in the plans so a bit of trial and error is required here! As I see it, there has to be enough pressure for the valve to remain closed under the operating air pressure, but not so much that it causes a noticable increase in pressure when being opened by the limit stop block. The springs could be made from hard-brass or phosphor-bronze sheet.