I have an old industrial 16 with a needle feed. It is truly a heavy duty machine. Mine was used to bind large leather bound books in a book rebindary. What I found works for getting thread is to ask the thread company and they are great to deal with. The canvas dealer may tell you what kind of thread you need. Some stock it. You will also have to decide if you want the thread to wic moisture or not. There are some good threads made for canvas and have uv protection. I can't remember the names right off hand. Waxed canvas is weird to work on. The wax will crud up your machine something fast and furious. You will need to wear gloves and old clothes and you will want to be cleaning out the bobbin area every single time you change the threads. It may take a bit of a solvent to get the wax out. I sewed two authentic reproduction army officers tents and 3 awnings out of Canvac a few years ago. It was a real mess.