Thanks, spud and all. My SG flip measures .530" outside to outside, so that's close enough in this somewhat imprecise test that you probably need either/both the drawings or someone to measure an IBM appropriate flipper. There's certainly nothing critical about flip sight outside dimensions, so a broad tolerance wouldn't come as a big surprise.

For general reference, a small paper clip is almost exactly 1/32" - so the discrepancy is about one fourth that on each side. Wouldn't take much of an undercut to fit my sight within your stake marks.