Hi there

I'm planing to build a reducing back for a old 10x12 wooden camera.
I know what are the critical measures to respect for the film to be in the plan of focus but before drawing the whole thing I wonder if anyone has plans for a 8x10 wooden springback ? Such backs are manufactured since at least a century and I'm sure there is no need to re-do the whole thing.
Plans in metric would be super-cool but imperial could do the job as well. I'll be very grateful for any help. Old drawings, sketchup 3d...anything ;-)

Thank you