You may have gotten BSed on the pull of barcons. I've yet to see any that wouldn't pull enough and I've seen some pretty old ones. If yours don't work,there are plenty that do, even old ones. FWIW, even the shimano index ones have a friction mode. Why don't you just use a Shimano XT 135 mtb hub and a 8 or 9 speed cassette,and a current shimano MTB RD that will have the big cog capability a big cog up to a 34 if you need it. Your life will be easier if you have to replace anything on the road. Wtih the shimano 8/9 hub, you can even stick a 4.5mm spacer on it and run 7 sheed HG cassettes if that is what turns your cranks.