Well, I ended up using this for our 50-miler today:
2 qts. water
1/4 c. lemon juice (Santa Cruz Organics bottled lemon juice actually came out to be cheaper than buying whole lemons and juicing them!)
7 T raw honey
1 T organic molasses
1/8 t sea salt
This came out very close to the 30g. carbs, 10mg. sodium, 100mg. potassium ratio suggested to me.
My water bottle holds about 28 oz. and I filled it up to the top. Drank a bit right as we started out, and then drank every 45 min. to 1 hr. (I think our ride time was around 3 hrs., but I crashed at one point 

 and that added to our total ride time). I had filled another 10 oz. bottle and froze it and left it in the car, but when we got back it had barely melted. Probably got about 3 sips out of that one.
Anyway, the homemade energy drink, coupled with getting up at 5am and eating hot cereal with raisins, an omega-3 egg, ground flax, and nutritional yeast flakes mixed in, eating a rice pasta/cannelli beans/spinach/onions/olive oil combo for dinner last night, and drinking lots of fluids yesterday made for a very pleasant ride today (minus the crash). No dips in energy and was able to keep up with the group.