If you're using Windows there's the possibility to add a directory at the first page in FGRun.
It's not the first page you see when starting FlightGear. You have to press the Prev
button to get there. TerraSync set up - FGrun's first page
by Johan G
, on Flickr
Low-level flying — It's all fun and games till someone looses an engine. (Paraphrased from a YouTube Video)