GSX obviously follows the exact same rules as FSX, the higher AFCAD in the Scenery Library for a certain airport will always take precedence over the lower ones, which means GSX will always use the most correct AFCAD automatically.
However, there are some thing in addition to check:
- The AFCAD must be "self contained", it must contain everything needed for GSX to work, which is the parkings, the taxiway layout with paths and nodes. A partial AFCAD, for example one that redefines parkings but takes the rest from the default scenery won't work.
- The AFCAD must be legal. If there are error or the file is corrupted, GSX won't use it and will revert to one that works (usually the default one)
- The path for your scenery in the scenery.cfg shouldn't end with \Scenery. FSX accepts it, but it's not the standard so, if you have paths ending with \scenery, remove the \scenery part at the end