Right, I should have been more specific. The plywood I have is called 5.2 mm by the big box. I haven't measured the size but calling it 1/4" is close enough.

Several years ago I worked in a custom furniture and cabinet shop. We often built curved pieces using luan core and heavy veneers. The luan first went through a sander. Resulting in a thickness that I can not replicate. The thin luan and solid veneer then was laid up on form built for that specific piece.

So bent laminations like this, I think, might be out as a possibility.

I think I like the idea of relieving the backside and filling it. A steam test resulted in delamination after several minutes with no appreciable effect on flexibility.

Thank you for your thoughts!