For any of the main outhaul, traveler or jib car control lines Kevlar, Spectra or Vectran core line is essential. Stretch is the enemy of performance in this application.
I tried 10mm OD Kelvar core line and found it insufficient for the use on the Andersen line tender drum. It consistently slipped under load. 12mm kevlar core works fine. It doesn't surprise me since Andersen specifies that these drums are to be used only with 12 mm line.
I can only say what I found on my boat. If 10mm OD Kevlar core line works for you, or has some advantages over the larger line that I do not understand, then do not let me talk you out of it. It is entirely possible that I missed some vital setup detail that would have made 10mm line work.
I adjust the position of the traveler and outhaul quite a bit when sailing. Having the control line slip when trying to pull the traveler to windward is a real pain in the neck.
Annapolis, MD, USA