My bike tracks to the right, must be a rare, "reverse" track model! Wheel dish is very close, I built them and used a campy dishing tool front and rear. I checked the string thing again, it's about 2mm off now. So many variables as you said - I'm going to just ride it now.
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"