Hello, I don't think this is true...
Yes, it is. All our installers are 100% fully compatible with P3D without requiring to do anything. In fact, if you DO something, you might screw up things.
If I use the normal fsx folder, I can't choose P3D for the installation and GSX installs for FSX by default
That's normal, of course. Since you told the installer there's just FSX installed in your system, the installer can't see P3D.
if I change fsx.exe path to P3D's folder (I rename Prepar3D.exe in fsx.exe), I get a message that I need fsx SP2 installed on my computer!
That's to be expected and it shouldn't be done this way.
If you have a registry entry for FSX only, point it to the P3D folder with a fake FSX.exe which in fact is still Prepar3D, it won't work either, since the installer is looking for an FSX version number on an FSX.EXE, it surely won't look a Prepar3D version on an FSX.EXE file.
So, I don't think we are able to choose
Yes, you are.
In any case, I didn't found how to do it.
Just by NOT doing anything. Which means, having the Prepar3D registry keys pointing to the Prepar3D folder that should contain a (real, not renamed) Prepar3D.exe, and the FSX registry keys pointing to an FSX folder, which contains a real FSX.EXE.
Which is the situation you should be, when simply installing both simulators, without using registry tools, migrations tools, etc.
If you are in the correct situation after a correct Prepar3D installation, you WILL see a question about installing into Prepar3D, and it WILL be correctly recognized.
An other problem is, that as I had to manualy move all the files for using it in P3D, afterwards in P3D, GSX is not using P3D' sceneries, but instead, it is using FSX's files (AFCAD I think)
That's normal too: if you registry keys for Prepar3D are wrong and are pointing to the FSX installation, GSX will look into the FSX scenery.cfg for the list of files used.
I repeat and confirm, everything works correctly in P3D, provided you don't start playing with registry and rename files, which is not needed, with any of our products.
