The return spring on my Pappas is of moderate tension, not light but not real heavy. I would think that to light and the gun would not be able to be aimed one way or the other (depending on what side you have your windage knob). On your rest do you have a bearing surface on the base plate where the elevation screw touches it to slide on? Or is it just on the piece of base metal? On both my Pappas and my VonAhrens there are bearing surfaces placed there to allow the elevation screw to slide easier on (not sure what material they are, but delrin would be good). That would allow you to be able to use a lighter spring for windage.