Replying to Backcountry ski length

So I live in southern Sweden and havn´t really been able to do much bc skiing, but next year I´m spending the season in the alps. So I need a pair of pow skis. Considering my backcountryexperience consists of hiking a hill with half a foot of snow and skiing down on Armada Halos I am at a loss when it comes to bc skis. Knowing myself I´m probably going to spend most of the time jumping of stuff and not spend one second on the trails so I really want a playfull ski.
I have pretty much decided to go with the regular JJ but I have no idéa what so ever when it comes to the length of the skis. I weight about 80 kilos (176 lbs according to some convertersite).
So what length would NS recomend?