I have not worked out the exact chainring and cog sizes you would need, but one way to pick up the lost "in between" gear ratios is to use a 1.5-step system, in which the ratio change in front is 1.5 times the average ratio change in back. I run 50-42/14-16-18-20-23-26 on the Bianchi, with the only drawback being the 84-to-96 gear-inch gap on top. A 7-speed freewheel with a 15 between the 14 and 16 would be one solution. The double shifts are not that bad, since you use them only for fine-tuning.
Also, if you don't really need that high a top gear (I don't), consider starting at 13 or even 14 teeth in back.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069