I tried a simple antenna today with pretty good results:
I've got a 7A tip up, and used a bulkhead BNC fitting (P/N ARFX1130-ND at Digikey.com) though the canopy frame that closes above the instrument panel (sorry I don't remember the Van's part number!). Obviously the bottom I attached to the tracker, but on top I used a 19.5" piece of 0.041 safety wire mounted in a BNC connector. The top of the safety wire was attached to the canopy with a small (1/2") suction cup. I was very happy with the track I got. Weather was getting down to 3 miles in snow showers, so I didn't stay out too long!!
This was just a test to see how well the antenna placement worked. I'll probably build another one and re-enforce it with some strands of Uni fiberglass which might eliminate the need for the suction cup.
This flight was over eastern Iowa at about 2500', so with the flat terrain, perhaps anything would work. But I'm happy enough with it to stick with it for now! If I hadn't forgotten my camera, I would provide a picture or two!
This is fun stuff!