I'm a veteran of TX heat and plan my hydration/distance very carefully.
There is
a Lot of There Out There in TX , being out of H2O w/ nothing but a very long empty road ahead in 105F heat index like today is not good.
Take what you need however it appears to the Pro-look Police.
I mount a double H2O set-up behind my saddle along w/ the two bottle mounts on the frame and whatever in my jersey pockets when doing long miles in summer heat.
I'm told it looks stupid by Captain Fast (who never ventures far from Starbucks) although I'm not the one out of water halfway back from Vanderpool....
If you add the electrolyte potion that works for you get different color bottles for straight H2O and electrolyte.
Dumping a bottle of sticky-goo over your head instead of water is not as funny as it sounds, trust me.
Start early, ride your own pace, learn to sip/eat with regularity on the move/change bottles on the go and limit stop times to get fluids/go with minimal chit-chat.
Have fun and wear sunscreen.
-Bandera