I posted this in your other thread in the Classifieds Section, but here it is again...
I have the 07 PEs in 169 and I originally had them at +5.5 from recommended mid sole mark which is -2 from core center. I was doing about 60/40 mountain/park like you and then I got much more into park over the season and now I'm more like 20/80 mountain/park and I remounted them at core center (+7.5) and I love being more in the center for riding and landing switch...I honestly don't feel a big difference between the two...One time I did was when there was some deeper powder and i was trying to turn real sharp, I could feel the back end of the skis dragging more than usual but it's no big deal, you get used to it...I would recommend +5.5 to +7.5 (core center)...it's a stiff ski great for all mountain and park so you can't really go wrong...I spent a long time thinking about my mounting these same skis so I hope this helps you out...let us know what you decide.