Wishful thinking doesn't make your on-hold ad a radio ad, so I think you have to forget about the 30-second exception. Rick's Guru response is 10 years old, and there's been a rewrite of the FDIC's regulation on advertising of membership since then.
An on-hold message is an ad, and it should conform to the requirements for inclusion of the "Member FDIC" and "Equal Housing Lender" tags for print ads, unless you can obtain a written opinion from the agency involved that it will allow you to treat it as a radio ad. I also suggest you avoid including deposit and non-deposit products in the same on-hold ad.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8