Keep it it Simple for yourself. Follow the Recipe and instructions for Sausage since you want to replicate it exactly, Go by Diggy's Calculator for large cuts , like Bacon and Ham. You will NEVER GO WRONG with 156ppm, per the calculator, when you get to the point you are creating recipes.
As far as your question, you need to stay in the safe range. The only difference Size makes, is how long it is going to take to fully cure to the center. Ground meat cures almost instantly, beyond that you can figure 1/4" penetration per Day.
Shannon has Decades of experience and was taught by family members that have used that recipe for Generations! You might want to get several pounds of Sausage, under your belt, before you try to develop a recipe and worry about saving a couple Hundreth of a Percent of Cure based on meat thickness. Especially since it don't matter what the size if you are using 156 ppm Cure #1...JJ