The V800/V850 ANR film holders are interesting. I bought the 35mm one on eBay because I was scanning negatives shot on a Unisex Mercury II, that had been stored coiled in a film can for 70 years. (Not my fault!) I put the convex side against the ANR "glass," which held them much flatter than the "open" film holders that came with my V750.
One thing to note is that ANR material is not glass, it's a plastic resin. Exceedingly easy to scratch. Very tricky to clean. My wife made me a quilted cloth pouch to store mine in.