This winter I finally bought a FLARM. I opted for the new Garrecht TRX-2000, which includes not only a FLARM device with graphical representation of the traffic situation, but also an ADS-B and Mode-S transponder receiver. A nice piece of equipment.
Both the ADS-B and the FLARM antenna need a ground plane. In my Libelle the only possible location for the antennae is behind the instruments, and since the antenna cables have straight connectors, I needed to elevate the ground plane a bit. Some scrap aluminum was quickly converted in what some might consider overkill (nobody will ever see those flush rivets):
