I previously had a Duopar Eco on my touring bike when I ran it in 3x6 friction shifting. But I switched it to SunTour Accushift with an X-1 RD, and XCD FD and Superbe Pro accushift ready 7 speed down tube shift levers and a Winner Pro 7 speed freewheel. It indexes nicely and inspires confidence more than pure friction.

The Duopar pulley cage is a wonderful engineering curiosity but I ultimately found it to not be easily servicable when the upper pulley wheel started to squeal for lack of lube. I sold it on eBay and never yet felt complelled to go back the Huret derailleurs as cool as they might be in theory.