Drop and cast adjustments for kid

[Blowdowner]

I already cut the stock for length of pull. But what generally do you do with the shim kit and comb for a small person 90 lbs. Surely there has to be a generic adjustment to make an adult shotgun fit a kid better. The distance from his shoulder to cheek, both vertically and horizontally is tiny compared to mine, as is the overall size of his face. I already cut several inches off the butt and fitted a new recoil pad, but since the stock is still removed I’m wondering which of these shims I should put on. Generally. And should I fashion a comb riser? What are some typical adjustments for all smaller shooters?