I agree with zoama about running a single instead of duals! Twice the headache, twice the welding, more weight, more to fail later, etc. Your fit up will have to be darn near (if not) perfect for fusion welds on that thinner material! I don't remember who gave me this tip, but somewhere along the line a friend or coworker clued me into taping latex (or vinyl) gloves onto the ends of tubing as "caps" when purging (or at least one end so you can see if you need more or less pressure to keep the glove inflated). I normally use rubber expansion plugs, but thought I'd throw that out there. It's easier to visualize the pressure inside the tubing with a glove taped over the opening, plus it's a one size fits all. Of course this may be common knowledge to people who weld tubing and fancy exhaust systems all day long....that person isn't me!