I can do whatever I want as long as I can get the blanks. Nobody who does wheels makes their own barrels, that includes HRE, Asanti, Fifteen52, basically if you make wheels, you dont make the forging, center or the barrel blank yourself, doesnt matter how big you are, unless your Rays Engineering, BBS, or Enkei. We all buy them from suppliers in raw, freshly spun, blanks, then we drill the holes and bore the center, then have them polished and/or coated/plated/annodized.
I know 2-3 shops that will do 13" barrels.