I did not read all the posts mostly because I think this is not a good idea. First of all, lead and the dust from the vibrating pellets is vey toxic and easily breathed in while handling or maybe even while using. This is proven science. Second, someone will someday cut or weld that area and have the same lead problems by years of vibration. A wild guess as well is wondering if the dust from lead can be explosive if a spark is introduced into a closed area. I don't think so but many other dusts are.
You can also use round barbell weights as an easy fix for many things. I made a bracket with a round post welded on and then just slipped on the weights needed. Works great. I don't care for the lead idea.