Yesterday while in Lowe's I happened to look at .500 copper pipe and it has gone back down quite a bit in price to about $12/ten foot length. Fittings are a LOT cheaper and a lot easier to cut and solder then trying to thread those odd lengths or fit with available and very expensive pre cut and threaded nipples and fittings. Take a pad with your parts list, get the costs and refigure and you will probably find that the copper is cheaper especially when you add in that time to go for more black iron pipe fittings.