Replying to Salomon 1080s - what length?

This is not a discussion about the quality of these skis, I've ridden them, I like them, I'm buying them.

But what length? Im 5ft8, weight 60kg (140ish lbs). I've found somewhere where they are on sale cheap but they only have 171cms. Would these be too long and would I be better off going for 161cms? I ski in the park, out the park, back country, everything really, but will be spending a season in whistler next winter so gotta be vaguely good in powder.

Any advice would be awesome.