I assume you've read the material on salt replacement on the Hammer website? With what do you disagree?
I'm a sweater, though I never measured the salt content! My longest ride so far was 18.5 hours in heat up to 104°. Endurolytes were fine on that as well as many other long, hot mountain rides. I often hand them out to riders who are having trouble emptying their stomachs in hot weather. I've seen riders in trouble with salt tablets (upset stomach, vomiting), but never seen anyone in trouble with Endurolytes - anyone who actually took them that is, as opposed to just carrying them
. My feeling is that if they work for the 508 and RAAM, they'll work for most folks. I don't know a single ultra rider who takes salt tablets, and I ride with a few, including a couple of champions, though I'm no great shakes myself.
Whatever electrolyte one takes, I do think it's important to separate electrolyte intake from fluid intake, as they are separate issues. Just if one is really going after it, that is. For "normal" riding, almost anything works fine.
In Hughes experiment of one, on the ultracycling.com website, I've always found that a couple of Endurolytes will help the stomach empty, which salt, as Ms. Barr states, will not. But mostly what Hughes did wrong was the 700 cal. drink. Should have been only 300, and also about 48 oz. too much liquid. Duh. The electolyte and fluid replacement article is old. Latest experience and studies contradict the CW that dehydration is really bad and you should eat before hungry and drink before thirsty. Latest practice is to eat to hunger and drink to thirst. And you actually get faster with dehydration, up to about 3%, because you get lighter. The most important thing an ultracyclist can do is to keep the stomach emptying, as rapidly as possible.
Which are the reasons that even though it's impossible to replace fluids or sodium as fast as they are lost, you can keep going just fine anyway. Nothing else makes sense.