This is a very useful point. One of several justifiable criticisms of the elderly and generally worthy VU meter spec is that you really only get useful information from -10 dB to +3 dB. I happen to also use VU meters to monitor the outputs of my digital soundcard, but I've chosen to set my digital reference level of -20 dBFS to register in the middle of the VU meters at -3 dB. That gives me up to 6 dB of peak above the reference level that can still be metered on the VU. Since the crest factor (ratio of peak to average level) of digital audio tends to be greater, it's a more pressing need to see those peaks, but I just may try calibrating the tape decks that way, too. Hmmm, I could just pretend that I was lowering my operating level to 250 nW/m (which is what -3 dB represents on my M-79), and then I wouldn't have to recalibrate anything.
Cheers,
Otto