You shoudl definitely be riding a 160. As snowolf said, NS boards have a longer effective edge than similarly sized boards from other brands. For instance my Heritage 158 has more effective edge than a Nitro TG 159 that I used to have.
15 NS Ripsaw . 14 NS Proto HD . 14 NS Cobra . 13 Gnu Space Case EC2PTX . 2013 Salomon Powder Snake
14 Now Drive . 13 Now IPO
14 Flow Hylite