Go to the Github release folder:
https://github.com/briankendall/devreorder/tree/master/releaseDownload DeviceLister.exe and run it locally on your PC.
This should get you the GUIDs of your attached controllers.
Take the sample devicelister.ini and "dinput8.dll" from the "x86" folder on Github and put both in your IL-2 game folder.
In the "[order]" section of devicelister.ini, write down the controller GUIDs which you got from DeviceLister.exe, in the order how you would like your controllers to appear to IL-2, one per line.
That's it.
You can copy devicelister.ini and dinput8.dll to other IL-2 game folders on the same PC if you have multiple installations, in order to get the very same controller order in every IL-2 game instance.
There's also an option to apply the device order system-wide as described
here, but I won't recommend mucking around with your system for an issue that usually affects IL-2 only.
Mike