I use 6 all the time when I'm polishing. The pad and backing plate get toasty after about half the car, but not so hot you can't hold your hand on it. 6 definately vibrates more than 5, but I've noticed that when it does vibrates really bad it's because the pad isn't perfectly centered on the backing plate. When it's centered I can easily hold the PC with 2 fingers on the back near the speed selector and control it if I so desire, I don't recommend it, but the vibrations arent so excessive that you can't do it.