After reading several threads, flatness doesnt count on stacks unless leakage is of concern. Alex K. workbook does count it, see attached. The second stack shows a flatness 0.6 which makes me more confused. In my case, i am looking for the gap on top of the assembly far away from the flatness of the bottom washers. Do i care for flatness?
How about concentricity control? not most suitable but it appears in one of our drawing. I suppose it gets treated like position since is a location control.