Thanks Drew. AN texture showing through is exactly the thing I wrestled with when using AN glass above the negative. That's why I eventually scrapped it. I guess you're right it takes experimentation with different kinds - unfortunately I just wish there was an easier solution (aside from my TXP trick). For what it's worth, when I enlarge 4x5 negatives it is usually only to 8x10 or max 11x14, and I can't remember the last time I needed higher than about grade 3. So maybe that will help.
Also didn't realize 2mm could potentially be strong enough for sheet film. That makes things a little more interesting. For the fun of it I will ask Schneider how big a piece of MRC glass they could do. They didn't bevel it when they cut it for me though.
Bob et al: Is it 100% necessary to be bevelled? Is this a safety thing? Or some other reason?
I also need to follow up with John Sexton - a few months back he told me he was about to experiment with a different type of anti-reflection glass that was supposed to avoid Newton rings. I wonder how that went.
M. Lointain: Shiznit for sure! My 35mm carrier for my 4x5 Saunders has multicoated ("Multi Resistant Coated") Schott glass (from B+W MRC clear filters). Love it!