you subtract initial (8) from the total (35) to get the mechanical amt (vac adv capped as you said). I'd want more than 8 initial which means the slots will need to be shortened to maintain the correct total which MAY be 31 instead of 35 on a magnum. With that finalized then lighter springs staying just under the pinging point at WOT then plug in your vac adv & staying just under the pinging point at minimum part throttle (high vacuum) at an RPM where the slots are maxed out as in out on the highway at a light throttle cruise. EDIT the light spring kit will change how fast the mechanical adv comes in & shortening the slots will reduce the amount of mechanical adv