lowering a ceiling to match another ceiling

[mound]

Mound, Here in New England we usually install strapping (sometimes called "furring"), so with that, you wouldn't need a "ribbon joist". However; regardless of strapping or not, with a ribbon joist at both ends it would be easy to pull a string (an eighth or quarter low) to set the new joists perfectly.

Thanks. The existing ceiling drywall is screwed right to the joists, no strapping.  (I'm in Rochester, not quite New England
    I'll see what the drywall guy prefers when/if it comes to it.