Federal PS pump-it-down mod?

I'm rebuilding the leaky Federal power steering pump on my 68 Barracuda/318. I figured while I'm in there I would see if I could de-power it like they do on the Saginaw pumps. Does anyone know if changing the shims on the bypass section of the flow control valve will work? Or do I need to attack the spring pressure of the flow control valve itself? If I have to change the spring pressure, would I want more or less?
Thanks for any help.