I am 170 and got the 65 mid, after talking to Dave Miller and Dave Good. I skied on it tonight for the first time, coming off a regular 9900 sl. The mid Nano skis really really really good. I would go 65 mid ride, with the 178 flex. Dave Miller gave me some fin settings which seemed to work well, which I can pass on to you as well. Either way, go with the mid over the regular. More stable, faster and turns better.
If you are still unsure, call Dave Goode.