Usher CP-63XX owners, have you added Lead Shot?

I am awaiting my 6381's to arrive at the dealer this week, but am curious how many of you that own speakers from this line, have added either sand or lead shot? After looking at the prices of shot, it is quite a bit more expensive than sand, but should not be as messy. Did you notice any difference in sound quality, or are these speakers already heavy enough?

Thanks