The solution I was proposing was to double up on the oring, put a smaller o-ring, that pushes the bigger one to the mating surface. The Maxim web link was showing the inconsistencies with the petcock. With the spring pushing the diaphragm out like that, the double o-ring will mate up, with enough pressure, so that it works right. With the original oring absent from the market, the original was a wedge shape one, that was hollow, so when that was pressed up against the mating surface, it was guaranteed to seal off the fuel from free flowing.