I personally have had every ski I ride mounted at -1cm from true center for the past 6 years because it is nice to have that extra bit of tip for stability when riding around the mountain, and at only 1cm back, it's a negligible amount when it comes to actually riding switch.
I'd never recommend anyone to mount a ski forward of true center, but for a park specific ski, anywhere from center to -2 or 3 while ride fine.