Hajo, one explanation might be your system recognizing the wider monitor correctly because you have the LG software installed. The software itself may not do any difference, the drivers within do. Did you have your 24" monitor drivers installed or was it a "standard monitor"?
I didn't install software for the 24 inch monitor. Windows picked it up. Windows also picked up my new 29in. LG monitor. Ran from the get go. I reset everything in game on the first clipboard video setting. Installed LG drivers.
At 2048 resolution it was close to the instrument panel also. I went back and set the resolution to 4096, FOV automatically set itself to 96. Restarted the PC and still everything in cockpit looks larger then when I used
the 24 inch monitor at 1920 X 1200.

As I said earlier maybe going from 1200 height to 1080 is making the difference as well as being an ultra wide monitor. Out side the cockpit aircraft and fields look normal???
Monitor is 2560 X 1080 so maybe the change in size has something to do with it.

My vid card is an Nvidia 970GTX.