J.,
Can only comment on 10-1/2 lb,3" forend 6ppc's.
I believe the bags ( front and rear) should capture the rifle's stock like an old catchers mitt capture's a base ball,this cradles the rifle solidly from a gravity perspective. One's shoulder should be immediately close and relaxed to the butt plate to control the recoil moment and to precipitate working the bolt and returning the gun to battery in a quick controlled motion.Free recoil guys have a different take on this.I have seen some horrendous set-ups on the line,and can only wonder at some competitors bag set up and competitive potential.Bags should be #1--conforming to the shape and rake angle of one's rifle and #2--soft enough to give a little and not spring board the rifle to a different horizontal or verticle plane upon firing.
Joel