Greetings! Here is what I got on this. First, I have no clue where they get those weight ratings that sounds wayyy off! I am 6' and 180-190 lbs on a regular day. Closer to the 180 mark now. I have ridden the SL-R in a 155 and a 158 with no problems. Size 11 Northwave boots too, no problems. For me the SL-R just isn't my board but I preferred the 155 in it. My wide stance on that board with the set back inserts put my back foot right on the carbon v's and it was super snappy. The 158 felt the same but a little soggier for me. You would be fine with either and I would let your riding or availability help you choose. I haven't rode the 161 and I personally prefer shorter sticks then some but I am sure if that's what you had to get it would be fine too!
Another sweet NS to check out is next years Heritage! The more time I spend on it the more I love it. Today on it was epic! For me I would rather have a 10/11 Heritage for everything but that's me. I am sure you would be happy with the build on any Never Summer you get!
I just wish they would make a SL/Heritage type of board in a true twin with centered inserts... ::nudge ::nudge VINCE! hehe