J-mo's are designed to be mounted at -3 from true center (binding matte placement, center of sidecut, etc), and that is the mount we recommend for all mountain riding. This ski can be a very good park ski (its what our team rider David Steele uses exclusively for his shenanigans), and for that use, mounting it dead center is the way to go. If you are going to be doing more of a mix, feel free to put the binders anywhere between there.
And if you're Landis, mount them forward of center.