Where do you purchase the aluminum form?

You might try a non-ferrous scrap yard in your area .....I have seen really
nice stuff of there for little more than scrap prices. I used to be able to
walk about the yard and look about but the insurance industry and the
lawyers put an end to that in most cases. A lot of the large scrap yards
have been gobbled up by the big national and international conglomerates. I
remember seeing piles of Al tubing rounds, squares, angles et al. Try
hanging out at the local tavern near the yard ...it is amazing what a few
beers will get you ..... this is in all seriousness .....

Take care ...Merry Christmas all ..... Tom Popovic KI3R Belle Vernon Pa.