i used to use a long string, but same old same old: come in too light.
Then i found adb's how to on holmegaards, and his def'n of a long string really worked for me: just long enough, like a brace height of 0 inches. To find true tiller and true weight, i like to keep bracing the thing higher and higher as i go until i reach about 7". By the time I can brace it 7", i'm practically there. Weight and tiller are true...and i'm a happy camper.
As soon as I can brace it to 2", i do so. As soon as I can get it to 3, i'm at 3. I don't have a formula yet, but I have found that the bows work better for me if I tiller this way.