Re: UNDER FRAME BAG - Game Changer
Richard -- For randonneuring I use a Bent Up Cycles seat bag, the large one I believe. One of its advantages is bottle pockets on the sides. I have two cages mounted to my seat; when I need more bottles the pockets on the bag are great. Pulling bottles out of the pockets, and putting them back in, is a very advanced move that I don't do anymore. (My avatar pic is out of date.)
When I need more storage I use one or both Fastback Double Century bags. If you like to use a hydration bladder the Fastback bags are very good.