Two things:

1) I use these on my Dawes as it did not come with braze-ons http://www.twofish.biz/pdf/StainlessCages.pdf They work well enough, but they do move around a little (and abrades the paint). I reckon a small section of inner tube to put between the mount and the frame to hold in in place would fix that. For that matter, if I were to build that bike today, I'd look in to seeing if I could get some bosses brazed on prior to powder coating.

2) When it comes to fuel and hydration, I'd say do whatever works for you. A couple of years ago I near baked myself while training for a marathon (too much heat + ran out of water). In short, if you're not sure if your route will provide ample opportunity to refill your water bottles, go ahead and rock your Camelback brand backpack-style water carrying device. It may not look C&V, but neither does heatstroke.