Adding a flight plan (.PLN) to an adventure

I could really use some help figuring out how to add a flight plan to an existing adventure. From what I can tell, it's more than just dropping a .PLN in the appropriate folder; it seems that a [GPS_engine] section must be added to the .FLT file, but I have not been successful in learning all the information that must go in that new section. I've used some well-designed freeware adventures to get this far but now I'm stuck.Thanks!