"do" for ditto is hardly unprofessional, It is an abbreviation with a long history and is generally well understood, I've seen it on drawings that were old when I stated work. It may have disappeared from new drawings where a member size is in memory and can be placed with a touch of a button, but back when we did our drawings by hand it was a useful time saver.
Michael.
Timing has a lot to do with the outcome of a rain dance.