I made cast ballance weights for my ailerons. I found that a good way to make a mold is to carve the shape you want out of foam then use it to make a plaster of paris mold. Be sure to let the plaster of paris dry a few hours then bake it in the oven for a while to be sure there is no moisture in it that will boil and crack the mold after you pour the lead.
I used empty cat food cans on my gas stove to melt the lead so I wouldn't ruin any good pots.
