I have started work re-modelling the existing Piper J3 Cub. An accurate drawing of the Cub is being used with kind permission from http://www.toni-clark.com/Default.htm for the orthogonal views in Blender.
I aim to re-model the fuselage, main wing, elevators - well everything including the interior. I will also add much extra detail gleaned from all the pix one can download from the net these days. I don't expect to make many changes to the .xml files apart from the odd strobe light, animated pilot's head and start-up smoke. The model is being used with the blessing of its creator David Megginson.
I have posted a work-in -progress report on the Blender Artists forum http://blenderartists.org/forum/showthread.php?t=177903 - which also helps publicize the existence of FlightGear.