The gap on my working FOCS is .004" on the right side of the twist, non-existent in the center, and .002" on the left side of the twist. Both sides.A set of Feeler Gauges. I dont have any so I cant check mine. @Rosseforp might be able to shed some light on the question. I'm curious if the gap remains constant end to end.
My Grande is .002" all the way across, my Mk1 is .005"