Only place I've found the 5-ply plywood in the cities is Rockler. (Not marine grade, but not just 2 or 3 ply either). Of course after driving yesterday half an hour to the south store, didn't buy any since they wouldn't rip it for me. Then another hour back to the north store, discovered someone had just come in and cleaned them out of the material. So then back in the car, and another half hour drive to their west store (we'd called ahead)and got the last 2 pieces (30" X 30") Must be a 1/4 inch plywood festival in town. Like I said...penance.
But then today I miscut the piece for the right side. Back in the car again, 20 miles south, and procured the piece.
Penance. (?)
Today in the hangar was more productive. Got the right template fitting, and made the initial sizing cuts to the plywood.
Lessons learned; don't hurry, don't work tired, don't keep working when you haven't eaten lunch, don't assume since your metal working skills are greatly improved that the same is true for your wood working skills (they aren't), really learn the other tools, and so on.
Paul Poberezny called it....educational. Roger that.