I suggested a possible ID3v2 solution at the very start, but no one picked up on it - probably due to the hatred of ID3v2 in the groups that I read. Anyway, the original suggestion is here:
http://privatewww.essex.ac.uk/~djmrob/repl...rmat_id3v2.html
Cheers,
David.
http://www.ReplayGain.org/
P.S. - Sorry I didn't respond to your original question, but I couldn't answer it.
If only ID3v2 tags didn't cause problems with so many (poor) decoders, I wouldn't hessitate.
The ideal tagging system (generally) would be ID3v2 at the END of files, but that's not likely to happen.
So for now, go with ID3v2.