With the Live Update released today, we added internal support for the new 747-800, in passenger and cargo version, so I removed the GSX.CFG posted earlier, since they are no longer required.
- Run the FSDT Live Update
- Be sure you don't have ANY previous GSX.CFG file you made or downloaded, either under %APPDATA%\Virtuali\Airplanes or under the Simobjects\Airplanes\PMDG 747-8 folders inside the simulator. If have such files, remove them, otherwise they'll take precedence over the GSX internal configuration.
This config also supports the usage of wheelchocks as an alternative to the parking brakes.