I still have a set of Soupy's for sale (shameless plug) I found when adjusting them, as you adjust one side and then go to the other you can feel it get tight. Thats when you know you've gone further than the other side. Back off a bit and it gets easier to turn. I bet you are within a turn or two of the other side.
I've also done the tighten all the way and then count turn thing too, but eventually I got it close enough by tightening till it got tight then backing off.