Yes. Maximize fluid intake and retention by consuming maximum absorbable amount of water and sodium, that doesn’t pose GI distress, from onset of exercise.
Maximizing water intake per gut limits is key.
Maximizing sodium intake per gut limits is also key.
One without the other leads to hyponatremia or GI distress.
Without doing both, you can’t be optimally hydrated.
Optimal hydration is required for exogenous sugar/carb absorption.
Sometimes, it’s physically impossible to stay sufficiently hydrated to sustain max carb intake rates. It becomes an optimization problem. The RP Diet for Endurance goes into this.
The literature suggests that 1-1.2L fluid per hour, plus 1000-1500mg sodium per hour is probably the maximum absorbable, on average, during exercise.
I had heard that @Nate_Pearson frequently drinks 1.5-2.0L per hour.
While I was MTB’ing in Tucson in April, I was happily consuming 1.6L per hour + 2400mg sodium per hour, and feeling no GI distress, not to mention wanting more fluid and sodium. Context: Average power for these rides was very low end of aerobic with normalized power of mid-Z2. Full sun, 95 degrees. Relative exertion affects absorption capability of guts. I’m 6’1", 210.
I have not looked into evidence for linking body size to max fluid absorption ability.
There is little, if any, link between body size and carb absorption ability during exercise.
These two anecdotes lead me to believe that my water & sodium recommendations in The RP Diet for Endurance may be slightly too modest or at least too narrow, for some folks in very hot/humid environments, and that the inter-individual variability in fluid absorption rate and gut tolerance is high and probably trainable.
Holding carb consumption rate constant throughout event is likely not optimal.
Higher carb intake is possible while well-hydrated. Take advantage, so long as it doesn’t compromise hydration maintenance ability. Solutions of 8-10% carbs do little to slow down absorption ability compared to 6-8%. Since fluid volume consumption will be high, there is no need to exceed 10% carb solution. Getting close to it, in first 3-8 hours may be optimal.
It is unlikely that 10% carb solution will be optimal 10-30 hrs later when >2% body water loss is likely to have taken place. 6-8% carb solution is wise, at that point.