I agree with advertising being a problem, although an ad for incidental publications from the publisher does have exemption. Here's a quote from the content standard for Media:
"Books, including books issued to supplement other books, of at least eight printed pages, consisting wholly of reading matter or scholarly bibliography, or reading matter with incidental blank spaces for notations and containing no advertising matter other than incidental announcements of books. Advertising includes paid advertising and the publishers' own advertising in display, classified, or editorial style."
However, there may be a possible exemption for "vintage" collectible materials, e.g. a 1900 Sears Catalog. When I inquired about the classification for collectible publications, I asked about the ad rule and got conflicting opinion on very old collectible Magazines, Periodicals, and Catalogs.
If there are ads (unless incidental for more comics to come), probably best not to use Media. Actually, I think you'll like the 1st Class rate and so will a Buyer.
Danno