Your analysis would seem to be correct about new fonts being more efficiently encoded:

17588 large.bf
15626 large.bf.new
9272 medium.bf
8502 medium.bf.new
6500 small.bf
6102 small.bf.new

My guess is that efficiency comes at the expense of ease in decoding, but I'm sure it's not rocket science.
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- Tony C
my empeg stuff