I'm toying with the idea of upgrading the Manitou QR shock on my HP Sport. I'm not sure why since it works great, but I guess I'm curious to see if there's something out there that will perform even better. I went to Manitou's web-site and they mention a Twin Tube Cannister option for the QR. What's a twin tub cannister? Would that be an additional cannister like on the Swinger 4 way? Has anyone added this option to their QR? If so, what does it cost and does it improve performance?