Today my friend who was going to help with casting the elevator weights couldn't make it, so after some powerful thinking, I decided to do it on my own. I'm purposely not talking too much about exactly how I decided to do it, for casting lead is potentially a very dangerous proposition. I don't want anyone thinking that this amatueur's method have any credence, or should be duplicated.
But all that disclaimer aside, it worked much better than I ever thought it would. I casted about a pound more per side than was necessary. I'll trim it up before bonding in, leaving still a bit more than necessary, to take account for the weight of the paint, and do the final balancing after painting, probably several years from now. Talk about planning ahead.