Per Unit Flatness Callout

Yes, they are two separate feature control frames.  As you have already found, the geometric tolerance command does not support per-unit flatness as a single segment so the only way to do it is to do as you have done already.  Include an upper segment overall flatness but ignore it on the report (right click the upper segment label and choose "Hide Selected Labels").  As a side note, we don't support displaying the CZ (common zone) modifier either, you need to handle that by constructing a single plane out of all the referenced surfaces.

Yes, they are two separate feature control frames.  As you have already found, the geometric tolerance command does not support per-unit flatness as a single segment so the only way to do it is to do as you have done already.  Include an upper segment overall flatness but ignore it on the report (right click the upper segment label and choose "Hide Selected Labels").  As a side note, we don't support displaying the CZ (common zone) modifier either, you need to handle that by constructing a single plane out of all the referenced surfaces.

"you need to handle that by constructing a single plane out of all the referenced surfaces"

That's how I've been doing those, so I'm good there. Thanks for the other info though. I appreciate it Neil.