In the book "Shooting the British Double Rifle: A Modern Guide for Load Development and Use" the author outlines techniques for determining procedures in load development on how to decide whether you need to increase or decrease velocity determined by the impact pattern. Do you use Mr. Wright's procedure?
I do like the idea of separate right & left targets and the overlay idea. A short story. I had a friend who sadly has now passed but did hunt a lot and never shot more then one animal with any gun always claiming once you shot something the gun was all used up so time to build a new one. He had a lot. Once built he would start load development. After settling on a load he would then go to the range once a week and shoot the rifle, 3 shots, no matter the conditions, at the same target with a clean overlay target. That way he had a record of the gun and conditions of that day plus a total group of all the shots over the whole year until hunting trip time. A little anal but it was his way. He felt this method prepared him for what ever the weather would bring on that day his rifle had to speak. It worked for him. He had a nice trophy room.