There is a Sachs freewheel for sale on eBay which has a tooth configuration of 13-30. The gearing is 13-15-17-20-23-26-30. And I'm thinking to myself...Setting that up with a double crank on a vintage bike (I'm not interested in modern compact crank arrangements) seems like a great alternative to a triple setup for biking in the mountains. The seller indicates this freewheel is compatible with indexed 7-speed systems. And I am wondering why this freewheel could not be used with the early Chorus Synchro RDs in a friction setup. Those RDs had an A-B setting specifically designed for freewheels with large tooth variances from smallest to largest cog which resulted in what Campy calls an open taper freewheel (as opposed to an acute taper freewheel where the tooth variance is small). Can I get some expert opinions on this? I have no desire to use the Campy Synchro shifting to make this work, so it's either friction capable or I'll just forget it. Thanks for any info!