When attached, picnic shoulder and pork butt are the front shoulder. The break is at the shoulder joint, putting the picnic lower on the pig, closest to the foot. The butt is attached to the loin. On a cow the "butt" would be called "chuck". My experience in making sausage is the same as Juanito's. 65-35 lean to fat ratio, maybe even closer to 60-40. I would not expect 80-20 to have much flavor. Side note, most people I made venison sausage for preferred almost 50% venison to 50% pork fat.