So, you've got a TT bike which has room for a drink bottle (size & shape may vary) on the down-tube, not on the seat-tube as well owing to aero-bollocks.
You want to carry more water, but you also want to carry spare tub[e]s, a multi-tool, tyre levers.
A behind-the-seat dual bottle launcher might work, but where do the tools go? Or sacrifice one drink bottle place for a bottle full o'tools.
Yes, I know Speed Concept has the draft-box thing that you can fill with rattly crud (dunno if it is even compatible with behind-saddle bottles, but I don't much care as I haven't got one), so lets assume any other bike.
Assume the option to stuff your rear jersey pockets with tubes, pumps, levers etc is NOT an option as you'll have just been for a swim...
So, what do you do to tool up for a longer distance race/ride when you want to maximise your fluid carrying options?