Ok thats grat to hear you are having luck with the spring, but the design of the pump chamber to me suggests otherwise... on the opposite side to the diaphram mechanism is a small metal plate which just happens to have the same size seating space as the dia. of the larger side of the spring.. it firs in easy and for assembly is easily secured with a small amount of oil to keep it located while the pump screws are put in place.. ill give this a go and see how things go.. given the design of the plastic diaphram washer the spring pushes against, i think i have made the right choice.. will let you know ..

Happy flying