you should seriously consider building a vortex. even with the standard frame I've flown it in pretty low winds (I'm not an exceptional flyer mind you). I know several people on the forum have built a vortex with a UL frame (myself included)... check out this thread
http://www.gwtwforum.com/index.php?topic=4150.0Even if you don't go for a UL, the vortex is a sweet kite, and currently my favorite to fly.