I'm planning on stacking 2) 500g ex-propane tanks horizontally on top of each other for storage. I want to run a line on opposite ends of each tank, from the top of the bottom tank to the bottom of the top tank. (I will weld in tank spuds). I'm planning on at least 3" lines. The easiest and cheapest way would be to use black iron nipples and a union, but I don't think I'll be able to get them to line up when I go to connect them. How have others done this? Hose with fittings? I've priced some out and the numbers I got seem pretty high. If there is an existing thread on this can someone direct me there? Thanks!