So I'm trying to install my new tank, but it's a pretty loose fit on the base of the DuD. The tank came with a couple of O-rings, which I thought were spares, but perhaps I'm supposed to use them? If so, how/where? They appear to be the bigger in diameter than the ones that came installed on the DuD, but same thickness, so I can't see how replacing the O-rings on the DuD with the ones that came with the tank would help. What am I missing?