Believe me or not, but I fixed the deteriorated mirror in my Speed Graphic Kalart RF. I managed to replace it with the gold-plated mirror from FED, it's smaller and not as thick as the original one, but it perfectly covers the optical path in Kalart, and gives beautiful contrasty pictures, yellow and blue. I did put it with shorter side to mirror holder with some cardboard spacers on the unplated side, not obstructing any light. After some precision alignment to ensure the full coverage, I fixed it there with some drops of super glue. It works and looks just fine, now I can focus about anywhere - and the golden mirror won't die soon, I think

Cheers,
Zhenya