Bought your scenery today and it is great ! (Hopefully you'll do some more *cough* Biarritz *cough* Orly *cough* )
I don't have a very strong system since he's becoming older and older, but an OK one (i7-3770k - not overclocked - and GTX670 with 8GB of RAM), and am flying the FSLabs. I manage to have ok fps to me (20-40) at any stage of the flight by any weather/time, maybe a bit less at night but that's just fine. I'm already playing with 1024 textures in my sim, airplane and weather engine. I manage aswell to get those fps at airports much bigger than LFRS such as LFPG from T2G etc...
However, I'm very laggy at the apron of Nantes (like really), this does only occur at the apron and only when I'm looking to its direction, and I suspect the kind of "lightning" to be the cause of it. I thought it was the dynamic lightning (since in my cockpit it's lighten just like I had the dome light on) but the issue still persists after disabling it.
Maybe a clue about what my problem could be, or some bgl or fx files I could delete to improve performances ? Thanks! I joined a few screenshots if that might help.
My order id is : 1773207
PS : I did the updates available on your site regarding the scenery.