How about asking the manufacturers directly, and posting the answers? I asked a rep several years ago, and was told the cores are not acid free- that within 3 - 5 years problems with acid burns would show up. So wrapping the core with another fabric might not be of value long term. There are archival sprays for preserving newsprint- wonder if they would work on the thicker cardboard. Probably better to go with archival foamcore?