The most difficult FS manouevre? (sp)
Forget flying inverted under a 747 in an F-14
Keeping an F-16 under 180kts and 1000ft and staying in control of it for a circuit on VATSIM (with a controller watching intently) is the most challenging thing I've done on FS. With careful use of absolutely zero thrust, two extensions of flaps and careful trimming, it's possible 

Even managed to fly dead level at a steady speed for a bit too (this is the bit the shot's from)
Keeping an F-16 under 180kts and 1000ft and staying in control of it for a circuit on VATSIM (with a controller watching intently) is the most challenging thing I've done on FS. With careful use of absolutely zero thrust, two extensions of flaps and careful trimming, it's possible 

Even managed to fly dead level at a steady speed for a bit too (this is the bit the shot's from)

Nice shot.
*Moves to Tracey Island*