Tony, it took me a few years and numerous sets of stage 6 heads coming through my shop before I had a reasonable handle on the number of oddball things that could be wrong with those heads.
So now when a set of those shows up I know to look at all kinds of things that really have nothing to do with what would be considered part of a normal prep job on virtually any other type of head. But I know these issues exist, so I look for them before I start any of the regular seat and guide work.

I’ve never seen any issues with the shaft saddle diameter before either, but now that I’m aware that this is a potential problem with these heads....... I’ll be sure to look for it in the future.