Why are so many push-pull pots split shaft? I actually haven't found any other kind. This seems sort of strange since (I think) split shafts are for push-on knobs... So it seems like when you pull on a push-pull knob you could pull the knob off. I have not found any solid shaft push-pull pots, even though it makes intuitive sense that you'd want to use knob with a screw you can tighten down... What part of the logic am I missing here? Where do you guys get your push-pull pots and what sort of knobs do you use on them?