Hi there, Yeah, this stuff can get confusing, especially if you're new. There's a lot to take in when it comes to the development world of X-Plane! In short, SimHeaven is using custom autogen, utilizing facades rather than the standard X-Plane 10 library of autogen objects, so what you see is not what normally ships with X-Plane and is why they are able to apply autogen on top of their scenery as a separate overlay scenery file. Facades are great for custom autogen, but they are not exactly optimized for heavy use. This can often times lead to heavy FPS hits, and is why Laminar opted for a different method to generate their autogen over facades. We have developed a way to apply the more optimized method to our sceneries, but this will not show until NORCAL is released. I hope this was somewhat (even if minimally) helpful in giving you an understanding of what's going on here, and welcome to the X-Plane world! I hope you enjoy it a bit more than what you're used to with MSFS.