A few thoughts: first of all, if you are REALLY losing 12 lbs, you are in a HEAP of trouble. You are talking about 5.45 liters of fluid, and that is life-threatening! So first and foremost, DRINK!
Second, although I LOVE hammergel, you will find a lot of pseudo-science on the ecaps website. I will take some endurolytes at times (seems like a LOT of samples being passed out lately, and I DID buy a bottle years ago) BUT the PRIMARY NEED is sodium. So you either need to eat a bunch of pretzels and such, OR take a salt tablet occasionally, OR add table salt to your drink. I have played with that, and can tolerate a small amount of added salt to gatorade. Take a small measuring spoon (1/8 or 1/4 teaspoon) and figure out how much you can add and still make the drink palatable. Actually, the best combo I've come across was a mixture of pretzels, M&M's, raisins, and peanuts that were given out at a century. Got everything: sugar, salt, fat, and a bit of protein...the major components needed.
Calcium and magnesium are lost in sweat...no question. I am just not convinced that you really need that much DURING an event. Ca and Mg supplements are a part of my daily regimen.
Decide what tastes best on the bike...PERIOD...and drink a lot. That matters a LOT MORE than the specifics of what is in it. Take a salt pill every couple hours (OR WHATEVER YOU FIND WORKS FOR YOU!!!) Please LISTEN CAREFULLY: when you read data talking about 7% carb solutions...or training programs...or anything else, understand the following: if it is data from a properly conducted experiment, you are reading AVERAGES for the POPULATION STUDIED! Now, some folks have to dilute gatorade 1/2 strength to keep it down. I'm on the other end. I can mix gatorade, cytomax, or whatever at stated strength, and then add another 25g per bottle of granular maltodextrin. That is the same as slugging down a GU along with the bottle, except that you trickle it in gradually, instead of all at once. My point is that WE ARE ALL A BIT DIFFERENT!!! So don't rely on population statistics for understanding a single human being. In my professional arena, I deal with the most complex system on earth: the neurochemical structures of the human brain...and unfortunately, some [or, at times, MANY!] of my patients DON'T READ THE RESEARCH to know how their brains ought to react to the latest miracle drug. I tell people that every patient [or cyclist!!!] is a research project with N [number of subjects] = 1...in other words, we can know EVERYTHING in the medical [or exercise physiology] literature, but until we try for a GIVEN INDIVIDUAL, we don't know anything.
As for gastric emptying, a large bolus [stupid scientific term for a BIG SLUG!] actually SPEEDS UP gastric emptying, as does COLD fluid. So, knock down a pint or more of COLD carb fluid all at once for maximum pleasure.
One person talked about fructose and having problems...others do GREAT with it. Many endurance athletes SWEAR by honey (around 40% of the carb in honey is fructose), and there is a company that markets a "honey" carb gel. Hammer focuses on "complex carbs"...as though linking a few sugar molecules is a huge change. Look at glycemic values of various carbs...white rice, flour, etc...this isn't glucose, yet the numbers are quite high. Anyway, my point is to EXPERIMENT on yourself...each one of you is a unique individual, with different God-given abilities AND weaknesses...and that includes training approaches, nutritional approaches, AND psychological approaches...
...DOC out!