I use pure lead, but most of my spoons are 3" and under. I can understand the thought and concern for something less forgiving in a larger version, but it isn't a factor with these smaller spoons.
The largest ones I've made were 4" long but those big ones can be done with bigger tubing. They are just copper and brass plumbing tubes cut to length and semi flattened in a vice. I then crush one end completely shut and pour lead in them before crimping the other end. (if that makes sense)
More jigging spoons made from brass tubing that's been semi flattened and filled with lead. The shiny scales were done using a sanding cone on a Dremel tool.
These are some of the spoons and blades that I've made using copper and brass tubing. They are made by flattening a piece of tubing in a vice leaving the desired size cavity to pour lead into. I then cut the angles with tin snips and smooth them out with a hand file.
LOL! Just being silly. I had this scrap piece of wire from making muskie baits and stuck a hot dog on it. What's funny is that part of me thinks it might work.