At 150 lbs you can go smaller than a 161. I'm 180 and I ride a 158 for all mountain, but even I could probably get away with smaller. You should probably be riding a board around 155ish for all mountain. It's all preference, but you could definitely get away with smaller than 161 if you wanted. For width with a size 11 I would stay in the 152-158 waist width range, but slightly narrower or wider you could get away with depending on your stance and angles.