Another thing to pay attention to is the hole size the tuners have to mount in. As far as lubricating the nut goes, you might want to try some graphite lubricant. It's a dry powder that works very well. Though, you might not be able to tell a difference, it might be worth a try. Another trick is to use pencil lead (basically the same thing as graphite lub). And yes, the higher the ration, the easier it is to be very precise when tuning.