Cardboard viewfinder for 50mm and 120mm in 6x6?

I am looking for the dimensions to cut a piece of cardboard to make a view finder for 50mm and 120mm in 6x6.

If you are talking about the Mamiya I wish I could help. I have the C30 and C20 but neither of these two lenses.

A cardboard mask would not be too sturdy and easily damaged. I would use thin aluminum or brass. You can use a nibbling tool to cut out the holes. Finish off with a file to smooth the edges. Then coat the metal with flat black paint.

I have Pentacon Six, 50mm Flektogon and 120mm Biometar.