to quantify this, i would start w/ 6 pounds, the reason being, you can scale 6.25 to12.5 to 25 to 50, w/ some minor tweeks, scaling is not strictly additive, anyhow
2oz salt, 6.25 lb shoulder, 2 bunches of onions, or just eye it up, .25 oz crushed red, pinch of thyme, about 20 oz h2o, if you want it cannot hurt to chop up some garlic and throw it in, 1 medium to large onion, i would food process the white onion to a pulp, do a super coarse grind, unless urn doin patties. this combination is difficult to mess up, the trick w/ this is the bitterness of the onion greens, that's why add an extra white onion, sugar content.