first off you skis should be bigger but if you want to just ride park and groomers dead center them, not indicated on skis, measure and find the center of the ski.
but "modern" is 2-3cm back from true center .
for starting park and still skiing every where go modern but eather way you will be fine.
im 5'11" 150 and ride 181's dead center all over.
pow skis are mounted normal though.