Apologies if I missed it but is there still no way to reload a flight model other than quitting and restarting MSFS2024 if you don’t have a source package?
(I’m modding the stock Robin DR400 to function as a glider tow plane - it’s working ok but understandably I need to tweak the engines.cfg / flight_model.cfg to get the tow climb rate in the right ballpark. The existing towplanes in MSFS2024 don’t tow effectively so this is a necessary fix for gliding in MSFS2024).