Note for the Mission Builders
A quick note for the few people using Mission Builder with some of these more complex sceneries.
I have Rhumbas mesh & most addon scenery in a separate folder structure - it saves on disk space when you're running multiple installs!
Quite often I come across airbase backgrounds partly obscured, as though the Sim is just reading mesh from within the Sim itself. This particularly affects multiple runway complexes, where adjacent runways are at slightly different elevations, but I've also seen it at island basees too.
It only affects the Map view in Mission Builder, not how it appears within the Sim, but as a result it can make placing objects well-nigh impossible. You can imagine the fun I had creating the gsl packages
I've discovered that in almost every case you can work around this issue by placing a copy of the runway A16N bgl into the CFS2/SCENEDB/RUNWAYS/SCENERY folder.
You need to remove this duplicate A16N when you've finished working in Mission Builder, as the A16N merging logic is quite crude, & you'll find it doesn't look so good flying in the Sim with the duplicate still in place. But it does flatten the runway area whilst you're placing objects during the Mission Building process.