Laser for you
At 170, you're about ideal race weight for a Laser, if I remember correctly, and going solo, you'll have a great, wet time. Taking along another adult, or even a child, will get VERY cozy, though. At my club, there is a teenage couple that sails a Laser together regularly, but I think they use the experience more as an opportunity to be physically close than to have what older adults would consider a pleasant sail. The Force 5 is marginally more accomodating for two.