Very good point, thanks for the advice!
In the SDK they say:
Default is 0.4 - which is about the perpendicular drag of a cylinder - and the value should usually fall between 0.2 and 0.8 for most aircraft.
usually between 0.2 and 0.8… Now comes the funny part…
I checked the MSFS ‘‘golden standard plane’’ Cessna 172 G1000,
because there I wanted to begin with the test…
Then I saw the value:
fuselage_lateral_cx = 4.3
freaking 4.3 !!! And they suggest 0.2 - 0.8 for the developer! 
I checked a few community and other MSFS base airplanes
and they are all using these low values around 0.4…
No wonder we have weird aerodynamic bahvior everywhere,
because with low fuselage values like this, the fuselage doesn’t exist in MSFS 