Do I ever!!! I have been working day and night trying to solve this problem in real world scenarios, for all people, using an algorithm that captures every single possible scenario.
In fact, jumping into writing the logic now.
The answer: it totally depends and here are some of the things you should think about. But first, the easy answer:
If you’re sweating moderately and are able to consume enough fluid to offset but not exceed sweat losses, then probably 0.9-1.3 L of water per hour would be great, alongside 1000-1500mg sodium per hour.
If you’re sweating more heavily? More fluid & sodium.
If you’re sweating so heavily that dehydration occurs because fluid & sodium intake can’t offset sweat losses? As much fluid as you can tolerate with as much sodium as you can tolerate. For me, that’s close to 2L/hr & 2500mg sodium per hour. But maybe higher. Still experimenting on the upper limits. Eventually carb consumption rate needs to decrease to accommodate decreasing gut function which happens with progressively worsening dehydration.
If you’re not sweating at all because it’s cold out and don’t mind peeing a lot? Somewhat less fluid and sodium so that you’re not peeing constantly. How much less is a very good question and probably personal preference. If you’re doing a 140.6 where peeing on your bike is cool, err up towards 0.8-1.0L/hr + 800-1400mg per hour.
If not wanting to pee, and wanting to push max carbs while trying to match but not exceed fluid needs, while cool / not sweating: it’ll be personal gut tolerances for concentration here, but I can say that my wife and I have done ~20% solution (500mL per hour) while consuming 100g carbs per hour, on cold rides lasting 3-5 hours. She’s done that concentration of solution for >10-hr rides too, but at a lower hourly amount just to avoid GI distress. (75-80g/hr).
Now to go put this all into code. 
I think you may enjoy using the app I’m writing.