I have the Revelate Designs Viscacha tail bag that holds quite a bit. That plus the large Revelate Tangle frame bag size large and the Revelate Sweet Roll handlebar bag would weigh a whopping 2.15 pounds according to their website. I made a real simple harness to hold any size waterproof stuff sack on the handlebar, and I think that weighs something like maybe 4 ounces on the high side. I weighed it once, but I forget. DIY ones are usually lighter because the mass market ones are overbuilt for durability. A gas tank would be an additional 4-ish ounces.