Hmmm. I do have some old Huret derailleurs that nobody on this earth wants. I'm going to measure first, to see if 60 inches is enough - it just might be. I don't think the solder thing will work, partly because of strength, and partly because I have no idea how to splice the things in the first place. I suppose I could cut the plastic insulation off the terminal block, and then just weld the whole thing together once the cables are in, as an alternative. A real actual cable will win the day though.