I fixed it. After a little bit of tweeking, I found the right numbers for a 1366x768-screen to be
Code:
<screenXY x="1" y="-200" xunits="pixels" yunits="insetPixels"/>
<size x="1366" y="1024" xunits="pixel" yunits="pixel"/>
in the end of the file. The cockpit gets a little bit stretched, but nothing serious.