Putting a softer spring in will cause it to bog the engine. It will basically be like being one gear too high. If anything, you would want to change the cam arms to ones without a notch, a higher total weight, but thinner at the tip. The notch is what causes the arms you have to snap in and at a higher RPM than a non-notched arm that was otherwise the same would. The high tip weight makes those arms shift hard at high speed requiring a stiff spring to counter act.
My 350 has Heel Clicker arms in it. My engagement is far lower than the standard 102C calibration. The Heel Clickers allow a setup that will not upshift quickly after engagement. It is like it engages, but stays in first gear until the RPMs come up.