I think that should work. Even larger formats could be scanned.

Write to Epson support. I happened to read in a report that the Fluid Mount can be requested free of charge when you buy the Epson V850 Pro.

I did the same and it worked (also from Switzerland). I could imagine that this could be useful for glass plates.

https://www.epson.eu/en_EU...

I bought the Epson V850 Pro a few months ago precisely for such scans, among other things. The tests so far (with Silverfast 9)
of 6.5x9 cm glass plates have gone quite well, but there is still room for improvement.

The formats worked. The distance to the scanner glass could be a problem. The film negative holders hold the negatives away from the glass and also have an anti-Newton ring disc.
But glass plates might still work.

Should be possible. I'm also planning a trial project. I'm going to make myself a mask frame. Let's see...