There is a difference between Hydration and Re-hydration and Electrolyte Replacement.

Most members here know this well but I do need to remind...
Sit back and think...

Did I hydrate?
Do I need to Re-hydrate?
Then consider electrolytes after your first liter of plain water...

Remember this hydration stuff is SNEAKY!

I can see the difficulty in trying to publish a reputable article in a semi-reputable journal on military electrolyte data. Here is a example of a mix I used as a medic when Air Born grunts were returning from the field in mid 70's SETAF.

Note: "In the field" is what we termed troops returning from extended "down range" duty. Officially no one was shooting at us... Ha. Further note, in the Army there are Air Born and there are Legs (Grunts). So what happens to the Air Born after they hit the dirt? They become Legs. After a few weeks in the dirt they are all Grunts.

So the mix goes and was provided to me via an up through the ranks E-9 Mess Sargent.

US Army 5 gallon Beverage Power Packet Lemon or Lime mixed with 5 gallons of water, 2 pounds of Sugar, and 1/2 hand full of Salt.

One of the biggest problems after returning from extended Field Trips was constipation. Couple of weeks of C-Rats or MREs with limited water meant not so friendly butt plugs. For that the Mess Sargent had a different mix. It was a Strawberry Powder Packet with 5 gallons of water and a heaping hand full of powdered pink laundry detergent mixed slowly so as not to foam up. You could have one canteen cup of the stuff after ya drank a gallon of the lime mix. I once asked the Sargent why use the Strawberry Packet. His reply was it would hide any blood... Ha. I just don't know of any medical journal we could publish this little method or would want to. Its quite possible this method only works on Grunts...

Here is my homemade (because I'm cheap and attempt all organic ingredients) mix:
2T Organic Tapioca Matlodextrin from Nature's Flavors
1T organic Cane Sugar
1/4 t organic pin salt
1 packet of (non-organic) True Lemon or squeeze of 1/2 lemon or lime. True Lemon packets are handy for taking along baggie of extra mix on long ride.

It tastes fine, has about 100 calories per bottle, and is not too sweet which leaves a clean feeling and not a sticky sugary mouth feel.

Looks about right. It's got flavoring for palatability, salt for sodium replacement (and, oddly, palatability) and sugar to promote water and sodium transfer across the gut.

Hooah!

It's been pretty well shown that cramps result neither from loss of electrolytes nor from dehydration. Cramps come from exerting oneself harder than one has trained for, or running low on carbs late in a long ride. As above, treatment is either pickle juice or mustard or Hot Shots. It's the taste, nothing else.

I separate my food, water, and electrolyte sources. Plain water, a high carb source, and Endurolyte capsules. I drink to thirst and encourage thirst by taking Endurolytes if necessary to encourage thirst, otherwise not. I can tell if I'm hydrated: I need to pee about every 3 hours. If I'm dehydrated, my HR goes up more than usual for the circumstances. If I'm low on carbs, my HR is lower than usual.

I'll use a high carb sports drink like HEED or SIS in my water bottles on short rides of 3 hours or less. Otherwise, it's plain water. If it's a long ride in the heat, I'll use a 2 liter Camelbak and possibly bottles. I never use Gatorade.

Again, you know you're adequately hydrated if you need to pee about every 3 hours. If the ride is less than 3 hours, don't worry about it. You're actually faster about 2% dehydrated because you're a little lighter. 3% however is not OK.

Another good tell is to watch your forearms. If they're damp, you're OK. If they go dry, you might have a medical emergency unless you get some water fairly soon. Sweat is the only thing that cools you. I've had my resting HR go as high as 120 from dehydration on a long 105° climb. Luckily, I knew where a tap was and sat in the shade and drank a couple liters of water, took some Endurolytes, was fine and went on.

Everyone is different about how much electrolytes to consume vs. volume of water. You have to experiment on yourself, but that's the big reason I don't have electrolytes in my water. No matter how much is in there, it's probably the wrong amount. I take 1-2 Endurolytes an hour if it's warm to hot. I have a riding buddy who needs 6. He's your usual slim, tough cyclist, but riding behind him in the heat, you'd think it was raining.

Weigh yourself before and after a long ride. If you hydrated and fueled well, you might have lost 1% but not more than 2% body weight. Eventually you'll learn your needs. (you will inevitably have some glycogen depletion and the water associated with it, so, some weight loss is normal. Weight gain is a big issue though)

I've never stripped down and weight myself after a ride, nekkid and w/o rehydration and refueling. Drinking a quart of restorative is the first thing I do. However the next morning I'll be light if that was a tough ride. It'll take me a couple days to put the glycogen and water back.

I'm usually 5 or 6 pounds lighter after a hot club ride with hills and chasing faster riders for 60+ miles. I did a mountain ride and tried to conserve water early (so I could stay with the group) and by the time I got to the next water stop it was too late. Got nausea bad and had trouble drinking or eating and was 11 pounds light at the end. Worst bonk ever.
Did the same ride 2 weeks later and guzzled water early and a friend sagged the ride with cold drinks and snacks and I had a glorious time.

I wouldn't think you would given your long history of endurance stuff. There are many others who are still trying to figure it out. If someone thinks they may have a hydration issue, weighing before and after is easy to do. 11 pounds lost can be 5-8% of body weight and since a pint weighs a pound the world around, that is like 5-6 bottles short. A couple pounds is no big deal. Some of that is depleted glyogen and liver

What has worked for me is starting out any ride hydrated. I seldom eat before or during rides less than 40 miles. I eat healthy. Cramping has never been an issue. I am constantly drinking water during my ride. I also use electrolytes, and an ice cold fresh green coconut water is refreshing too.

Nothing beats chocolate milk. It has everything your body needs.

Your mileage obviously varies. Chocolate milk, for me, means a mandatory 30 minutes in air conditioning to let it settle; otherwise, I'll get digestive tract problems when I resume riding.

Chocolate milk is fine for after the ride. That said, I can eat nearly anything on a ride, within reason and depending on how much climbing is ahead. When I was younger I had more trouble if I ate too much.