With your weight, I would only go 171. Im about 40 pounds heavier, and on 176's. I could easily take on a 181, as long as it is soft. Im on 176 Ar6's, which is a perfect size for me.
Even if your centre mounting, 171. 176 is total overkill. Dont fall into the "long skis are better" because at some point, long it too long.
With my most sincere regards,
"Skiing should be more like other "action" sports in which there are many different styles and ways of going about it all in which are accepted..make sense?" -powfoka