Yep, trial/error was my route there too. As i needed at least 2-3 m back then did i the 5-6m wire as a test as longer wire = easier to get located nicely. I had in mind that it may not work, but it have worked just fine. As its a “normal, but 6-core phonewire” had it been easy to cut and add a new RJ-plug at the end if it not worked. 