> It's actually quite difficult to hold a brake cable in tension, while forcing an old school front derailleur not meant for the bike into millimeter perfect po

> It's actually quite difficult to hold a brake cable in tension, while forcing an old school front derailleur not meant for the bike into millimeter perfect position Maybe you are missing the tension adjustment screws on the Bowden tube? You ajust the tension if the cable as close as you can with a pair of pliers with one hand, and a screwdriver to lock the cable in the other. The you use the fine adjustment screw to precisely align the chain over the cogs.