I am in training for my first half-marathon and looking for opinions from those who use, or have used Camelbak hydration backpacks for 21K + running. I am thinking I may need a 100 oz backpack. Did it take a while to get used to the weight of the backpack when filled? How has it held up during training and race day? Have you, or did you experience any chaffing from the backpack moving around etc.? Have you been pleased with the accessibility of small item storage (for gels and the like) during the run, negating the need to stop and remove the back for access? Have you experienced any bad water after taste from the bladder? Has it been hard to keep clean? Currently, I have been using a Nathan hand-held, as well as a Govivo hydration belt (which holds (2) 9oz bottles). I don't think a 21 oz hand-held is going to be enough for longer runs.