Stripped solid core cat5 is a very good wire, often I have used it as a starting point thinking i will find better down the track, but after trying many cables, guess what sometimes the cat5 won out. As for twisting, its always trial and error. As you guys know what seems to work in someone else's setup, may not in your system. I have found the diameter of cat 5 solid core to be about right in most internal applications.