You yourself have the exact problem you encounter, so tailor a curve to your own liking.
Start say, by using the Moderately Fast curve. Since you're reaching 127 too easily (and never want to hear it again?), pull down the rightmost point some (until as hard as you can hit say Middle C and nearby is acceptable). Then you've got your basis for pulling down the points leftward of that output level (none should be higher than the rightmost, let's say).
Working in from the other end, if Moderately Fast's influence quietens as soft as you want to play overmuch, pull up the lowest inner point (your very leftmost point should be zero volume) until it's passably soft for you, then you have the basis for making points rightward of that as high or higher.
And of course make the leftward working-in-adjustments (louds) meet the rightward working-in-adjustments (softs) smoothly in the middle. See how that all results, for you.
I believe Pianoteq interpolates between points curvewise, not straightwise. And a click between existing points will insert a new point between, which can be dragged around until perfect and removed with a double-click.
But don't believe me till you've seen it work!