I sometimes fly with the NGX and fsp. Some things works, some not. Real problems are with turbulence(no effect on aircraft) and minor failures - isolated electrical failures don't seem to work, for an example. Major failures like engine fire and birdstrike work. About your crashes - it is a pain in the &@($* to make fsp work with addons. Check your event log after your sim crash- that way you can tell which module is exactly failing and adress the problem.