I'm a little curious why no one has mentioned this yet (and perhaps I'm the one missing the point?) but what about installing a pressure regulator?
I use a Carter M6902 mechanical pump here, and even though it's advertised as 6-7.5 PSI sometimes it would peak over that...now it is set to max 6 PSI.
two reasons i give up on this was finding a regulator that i thought was good with a pulse pump (not saying there aren't any, i just didn't know which one to choose), and cost to do it all. i figured it might cost about $300 to do what i wanted and using a return line to regulate the pump was only a few bucks. if someone feels comfortable with a regulator than go for it. to me it's just something else to go screwy.
