Doug Mann posted a thread on his cradle here:

https://www.doublegunshop.com/forum...at&Number=519758&nt=2&page=1

Basically, he uses a couple of thick leather cups with leather padding the bottom to protect the ends of the stock.
When I made mine based on Doug’s design, I traced the outline of an extra large Pachmyer pad for the buttplate. I figured that would be bigger than any stock I’ll ever do. I did the front cup 2” diameter. After setting up a stock I wedge some scraps of leather inside the cups for some extra protection from the stock slipping.
FWIW, since it sounds like you just getting started checkering, ACGG member Mike Ullman is teaching a checkering class at Tishamingo this summer. He also has some YouTube videos.