I'm home now, and here's my notes and the recipe I used:
7 cans of lemonade concentrate
Sugar to an SG of 1.100 (1.5 pounds per gallon, more or less- see below)
water to 3 gallons
3 tsp yeast nutrient
3 tsp yeast energizer
3 crushed Campden tablets or 1/2 tsp K-meta
Wine yeast
Seems to me that I made 5 gallons of this, not three, so I must have used more lemonade, sugar and water. I used Cotes de Blanc yeast, and it fermented completely dry. This was WAY too tart for me, but my husband liked it so I bottled 1/2 and sweetened half. I sorbated/sulfited and then sweetened with sugar syrup. Yes, I think you should start a new starter, gradually making it more and more acidic so you don't traumatize the poor yeast! I don't know about gypsum as I've never used it- I just always use my tap water for everything.
By the way, this molly-coddling was well worth it. Everyone loves this hard lemonade.
Here's my notes- if they're incomprehensible, let me know and I'll try to figure it out:
What I did on 5/6/06:
In 1/4 or so warm water, sprinkled cotes de blanc yeast. Added yeast nutrient. When looking and smelling yeasty, I added some sugar water and lemonade mixture. All the sugar was disolved in about 1/3 of the water, with a can of lemonade mixed in. I added 1/4 c of this mixture to my yeast mix, and then added some more water and lemonade to the primary so that about ½ the water or less is in the primary with all of the sugar and 1/3 of the cans of lemonade. I took some of this out of the primary and put it in a measuring cup, and Ill gradually add that to the yeast. Ill add the rest of the cans of the thawed lemonade and the rest of the water tomorrow. S.g is 1.080, at the start after all ingredients are added. On 5/13/06, s.g. is 1.064, on 5/18/06 s.g. is 1.046. It hasnt changed much the last few days, so I racked it into 5 gal carboy. Not much sediment. It is fermenting well, room is 63 degrees. On 5/28.06- siphoned some off and drank. Very good, but still fermenting as well. Did not check s.g. On 6/3- racked into 3 gallon carboy, drank the rest. (some sweetened, some not. s.g. is .990)