Hi
Be aware that you can also get intersample peaks which don’t always show up on daw meters. I don’t know all the technical stuff but it has something to do with waveform sample points and sudden spikes on the waveform in between the sampling points. This could be the problem with your own hot mixes. There are plugin meters available.
http://www.stillwellaudio.com/?page_id=33
http://www.solid-state-logic.com/music/x-ism/
Try both of these on you own mixes. They seem to give slightly different results but can be useful.
Cheers