Hello David,
I've made a Clayton wagon and two of my own Q1 design with this design of valve gear and I don't think there are any 1/16th holes in the plans. You may be misreading the drawings, the only dimension of that size is the recess depth where the slides are set into the carrier part.
If you look at ME4381, July 2010, I describe how to make the Joy slides with plenty of photos. The Clayton used the same arrangement but upside down.
Regards
Nick