I'm 5'10" and 165lbs size 9 boots.
Last year, I had a Nidecker Ultralight 163 I it worked well for me in everything. I think with the camrock profile it definitely rode small...it was also not very stiff.
This year I've only been on a Rossignol XV Magtek 163. Has a similar hybrid camber profile and effective edge but is a lot stiffer and I remember at the beginning of the season thinking it wasn't as nimble in the trees as I would have liked. After 25 days on it, I don't really think about that anymore and I'm still liking to board in general.
I'm considering a Flagship (Carbon in particular) but am debating on size between the 161 and 164. In the end, I must admit that I spend most of time at my resort (Fernie, BC) so am thinking the 161 is the safe way to go for riding trees and bumps. But then I start thinking the extra edge would be nice for carving and do even better on cat trips or deep days.
Can't get demos on a board like this (around here anyways) so for the cost, its a bit of a gamble and I thought I'd check here to see if anyone had first hand experience. Maybe even comparing to other boards? I've demo'd a BSOD recently and could compare to that as well.
I'm 5'9" and 150lbs. 9.5 boot.
I've owned the Carbon Flagship 161 last year and this year I sized down to the 158. I prefer the 158 over the 161 in every single way.
I was worried about losing float and the like. However, I didn't have that problem. At your weight I'd go with the 161.