Interesting. Thanks for the insight. Yes the price of optical glass is pretty frightening, which is part of the reason I posted this. It was quite reasonable for my 35mm carriers but if I wanted to do the same for 4x5 I can only imagine how ridiculous the price would be for coated glass from Schneider/Schott, if they'd even do it. I guess I'm hoping there is simply no reason to go there, so figured I'd see what people thought.