Stickman that is an almost impossible question to answer with hard numbers since wind is only just one part of the equation needed to provide that lift. The angle of the wind to the hill or ridge line is critcal as is the shape of the hill and its gradients on the way to the peak or ridge line.

For every great ridge site There has been one brave sole who was first to prove the hill.

Pick your selected hill that has enough room on top to land as well as space to land at the base for your first attempt.

If its a ridge line I use to prefer that the wind be within about twenty degrees of being perpendicular and I preferred a hill that had a gradual rise rather than cliff like.

John