I've been mastering projects to peak at -7db RMS lately, but I know that a ton engineers think this is way too loud. I can get about -4db or -5db of RMS range in the song, with -11db or -12db being present at the quietest parts and -7db being present at the loudest. Most of my songs are averaging -8.5db. I recall Bob Katz saying -10db was acceptable, but not much more. Of course, Metallica's Death Magnetic was peaking at something like -3db with an average of about -5db. Anyway, I would welcome the community's thoughts on peak RMS levels and average RMS levels for a mastered recording.