Where to mount park skis?

I have a pair of 169 public enemies that i'm going to be mounting for purely park use.
Where do you guys recommend that I mount them? also, while i'm at it what, is the difference between "core center" and "mid-sole"? I measured the running length of the ski and divided it by 2 and that is where the "core center" is marked. So what is the mid sole? Right now they are mounted so that the ball of my foot is over the "core center".

Thanks.

Bump..., I just want to know if I should move them dead center or still keep them a little back?
Any experience?
Thanks.

For purely park, you want to have them mounted core center. Core center means that the center sole line on your boots is directly over the center of the ski. Doing this keeps you more stable in the air when spinning, because you have as much ski behind you as you do in front. If you spin a non-centered ski, there's an asymmetry in the mass and the length, which will result in a wobble. However, a center mounted ski will not perform as well outside the park, so many people compromise by mounting somewhere between core center and midsole. But as you are saying, you are using these skis for park only, so core center is where you should mount, no question.

Thanks.

hi all