What a question. Do you see any lip to keep them from walking? There are none except on crank. Tension alone does it, that's why it must be RIGHT, not your guess of right. It should be obvious to you by now that you cannot just tell tension right/wrong by feeling it, so quit throwing it out there. The tensioner has a range that the pointer should be in, if not it's just plain wrong. You adjust tensioner to get it in the range while bolt for it is loose, then once you are in range tighten tensioner set bolt. While setting tensioner in the range turn the engine CLOCKWISE. After that tensioner not adjustable since locked down but no need if it is in the range. Belt can wobble a little and still work. As far as belt riding on edge of pulley, someone has already answered that. Don't expect someone to guarantee you that an extra .005" or so either way is going to make you or break you. Keep second guessing or ignoring what everyone tells you here and before long you will be by yourself.