I do lead molds and lead casting at work Lincoln 7,it may be a tad heavy for the cockpit.Someone told me you can melt down aluminium with a crucible on a fire,but theres some sort of powder you add to get a good pouring.

Yes, I too had to take the dross off the top of the lead, I used to do a lot of Sea Angling shore, and boat, and made a lot of fishing leads for all our team, I did it on the gas stove, once you get a SMALL amount melted, you can put larger bits in,

If you go down the same route as i did, you won’t need me to tell you to wear thick gloves, preferably a leather apron etc.MAKE SURE THE ALUMINIUM IS BONE DRY, DON’T EVEN THINK OF TRYING TO PUT IT IN A CRUCIBLE EVEN IF SLIGHTLY DAMP, it will explode!!
Sorry I can’t help on the aluminium side, but I wouldn’t think there is a lot of difference, never heard of having to put any sort of powder in the mix though. Tried Googling it?.
Lincoln .7