This thread is pointless because there is no way for us to tell you where YOU would prefer your skis mounted. PERSONALLY I like ALL my skis mounted at -1cm from true center. BUT lots of people ski their skis at true center, and love it. Lots ski them at -2, -3, -2.5. Generally I would say mount them somewhere betwen center, and -4 from center. But, that isn't gong to help much becasue it's all what you prefer, and this YOU will like for YOUR style.
All of thos places are acceptable. The people who mount farther back, are going to tell you to mount back, and the people who mount center will say nothing but center.