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.
14 NeverSummer Proto HD . 13 Never Summer Cobra . 12 Gnu Rider's Choice C2PTX
14 Now Drive . 13 Now IPO
13 NB x 686 580