Thanks for letting me know. I won't mess around with the shims except as a last resort. Infinity focus seems close but not perfect.
FYI, the original screws from the old mount were standard, not Phillips. They had tapered 45-degree countersink heads. It seems like from your instructions you expected them to be Phillips head. Also, one of the new screws doesn't "bite" going in, so I think I may have a stripped hole. I pulled out the first new screw I tried in that hole and used another to the same effect. Even though the whole mount feels pretty flush and solid, that's probably what's creating the slight blur at infinity.