That would be a HUGE help, Steve! I've been looking on the Pingel and Z1 Enterprises sites, and though Z1 has this nice, simplified chrome one for $13, it might be hard to figure out which one I'd need if I don't have one on hand to measure. And Pingel's are about $100, and that's just not going to happen. Worst case scenario, I get one of those beer can hats, and just rig the straw up to the fuel line, that way I have one regular tank and a reserve tank as well! I'm planning on selling the original tank from the Twin on Ebay, and it's full of gas at the moment, so now would not be a good time to try its petcock on the new tank, and if I can avoid taking that one off, I will.