I have been using the "MSFS Legacy Importer" a freeware tool that converts old FSX aircraft into the current MSFS format. Worth a google search if you want to try it out. I can get a few aircraft to show-up using this tool but some have missing cockpits and/or the flight model is stuffed.
Thankfully I DID manage to port over my FSX vintage Real Air SF-260 which flies well, stalls and spins. Much nicer to fly than the default aircraft IMHO.
Always remember to switch between MODERN and LEGACY flight model if you do port over an earlier aircraft. I keep forgetting!
Good luck
TrafficPilotUK