It is good to find a light wind board that you can rely upon for good performance in the light stuff. Also, it can be fun to switch around from your light wind marvel to skimboards and surfboards to work the low end. I weight a more than you at around 190 lbs. and use a fairly large twin tip (148 x 46) which rides a lot smaller than it looks.
From:
http://www.extremekiteskiteboarding....opic.php?t=313
If you are looking at twin tips, I would say to find something fairly large, with little rocker. Fins can be important but once you are up on a big tt they may not make a lot of difference in straight travel.
Unfortunately, I am out of touch with current models having picked this one up a couple of years back. It is still doing quite well for me on the odd light wind session. Hopefully, others with hands on knowledge of current boards will toss out some opinions.
Boards are very important for performance at the low end. So is kite tuning, the point of flight line attachment to the pigtails, don't ignore that.