"Borrowed" from Teamkitfox.com: For what it is worth, I was informed several years ago NOT to double swage cables. The reasoning behind this was that unless done perfect there would be more slack in one piece of cable between the two swages. This would allow the two pieces of cable two work against each other and cause them to loosen. Example: between your hands hold two pieces of rope and leave one looser than the other and then try pulling on the two and after a while they would both be the same. The question then would be did only one let the rope slide or did both allow movement? I was told to take the time to do the one properly and you will never have a problem.
Also Skystar issued an SB a few years ago reference stainless cables and copper sleeves having compatability problems and having builders replace them with zinc coated sleeves.