I had a rather large cutting setup given to me a couple of years ago. The guy who gave them to me was a boilermaker, and had used them for work. The Oxygen tank is 244 cubic feet. Acetylene is maybe half that. He told me that he didn't think they would refill them for me without certain certifications. Is this true? How big will they do for a hobbyist like myself? I imagine that they will take the bigger tanks in trade for whatever size I can get. Who is the best place to use?