I do it on my Mac with FS4 as I did with FS2, and I don't need a "customer" folder:
- /Users/username/Library/Application Support/Aerofly FS 2/scenery/...
.../images/continent/country/... - /Users/username/Library/Application Support/Aerofly FS 4/scenery/...
.../images/continent/country/...