I use the NeverReach system and have run across the same problem. If the weather is hot, I will always go through 64+ oz in a half IM bike. I use a bottle cage to hold the empty. Alternatively (esp. if you are worried about the aerodynamics of a bottle cage), you can just put the empty bottle in the back pocket of your jersey (I doubt an empty bottle behind you will make any difference in aerodynamics but it might be uncomfortable if you are not used to it). I wouldn't suggest trying to refill the NeverReach in the aid station area (twisting around on your bike in a crowded section with wet pavement doesn't sound like a good plan to me).