The pages, safe flips and airtites I use are all PVC free and flexible, (supposed to be anyway) except that some of those stiffer safe flip double pocket holders do tend to crack at the seam with age and handling.
They look great---must be slightly heavy, but for airtites and slabs, that is a fantastic idea--an alternative to albums, if one does not want toning. Anything I put in an album, I am happy to have toned, but some folks don't want that--great alternative!!!!
I agree that only if you have storage devices cardboard free will you ever be free of toning. I like the pages posted above, and would probably use them if I wished to do a US series. For the "rest of us", 2x2's are about the only option because of inconsistent sizing of our coins. Btw, if using 2x2's, only use "modern" paper for the inserts, and never manila. Older white paper was created using the acid method, which will contain sulphur, and all manila contains sulphur. Only modern, (last 30 years), white paper is safe. This is due to modern white paper being made with the base method, in which more than half the paper weight actually being clay, and not wood.
On their site, Whitman sells pages for their albums with sized diameters, with all widths between 14mm and 45mm, so you could theoretically find one of those to put Air-Tites in.
What size half dollar airtities fit? Are they the direct fit or are they the airtites with rings? Also, do they tend to want to rotate in the pages or are they pretty secure? I considered that with Dansco pages and even did some experimenting. It turned out the pages weren't thick enough to work.
I've toyed with getting Eagle commem albums, which are either half or dollar specific. Hard to believe how difficult a project this is...