As a matter of fact, Shawn, I just got my pH tester in the mail yesterday. Since I've always wanted to know, right after I calibrated the thing, I tested a bottle of DB I had made in October, following the original recipe.
pH = 3.07
And you are right. That kind of acid needs to be balanced with a little sugar. It doesn't have to be a lot.
Uvas: Make a batch and do some bench tests for required sweetness. Not many people (no one I can think of) drink it dry. Like Shawn said, it needs balance. Start with a little sugar and work your way to what you like. It may take as little as one cup for six gallons to please you. You may not need what others add for your particular taste.