Sam,
Perhaps Laszlo's suggestion fixes things for you. If not I have attached the mask object (AC 11 USA) for you to try. If it works for your needs...great. In addition to masking interior elevations it can also provide a consistent outline for each elevation, space your notes, and ease layout on your sheets depending on how you set things up. There are notes provided in the UI.
I wouldn't mind hearing how others deal with interiors in their work flows. It seems to be a serious week spot in the documentation tool at they currently exist.
BTW you should create a signature with your version of AC,machine specs., etc. It can affect the answers you get.
Erich
AC 19 6006 & AC 20
Mac OS 10.11.5
15" Retina MacBook Pro 2.6
27" iMac Retina 5K