Join Date: Nov 2012
Location: Louisville, KY burbs
Hi, nichoth, I am also in event production. Could you describe the reason why the insides of the cases must not have any fasteners penetrating them?
I would really think about drilling shallow holes in the inside of your panels so you can sink nuts into them, or install pan-head machine screws from the inside if you don't mind having nuts exposed on the outside of the case.
Either of these ideas will be a lot more expensive than rivets or wood joinery, but honestly, you need a solid way to attach corner pieces to your cases. If you don't they probably won't last very long on tour.
Making a strong rabbit joint in 3/8" plywood sounds hard. I'd think you would need to use a hardwood plywood so the tool doesn't tear rather than cut.