As stated above, I'd already tried FSInterrogate with the same results.
Well, actually I did also test it with 3.30, however, I mentioned it in order to show that this presumably wasn't a bug introduced with the newest version :wink:.
However, I probably figured out the cause of this problem eventually. Obviously, FS9 does only init these values after you have started a flight, i.e. they are initially set to "0" whilst in the main menu for the first time (had always checked out the values while being in the menu till now). In FS 2002, they were already set after selecting the aircraft in the menu interface (as far as I know/have tested), so I guess that's the cause and probably there's nothing you could do about.
Thanks for your efforts anyway, Pete! Keep up the great work!