Here's a side view drawing of what is going to be 50'+ of seating for a new restaurant by the name of Haiku on the Drake campus. Plywood? Hell no. The backrests and seats on this installation will be solid 5/4 white oak.
Bob and I tore through over 200 bf in the planer with a couple of passes on table saw as well for preparation of glue-ups tomorrow. 2x4 frame construction 16" on center is probably overkill on something like this, but that's the way I want it. Besides, who's to tell me I'm wrong? I've been accused of over-engineering before...and I honestly don't mind it.