For my earliest prototypes I used copper sheet snipped into strips and glued on to the bottom of the balsa bodies. I was living in Sweden at the time and could not find any lead in the big stores. I was living in an apartment with limited cooking facilities and a VERY sensitive fire alarm hooked up directly to the fire brigade, so heating lead was out of the question.
My one attempt at cooking sausages did not go well and was not enough to go round the crew of the two fire engines that was called out. Also they were the most expensive sausages of all time as I was billed some $2000 for the service.
Dave