Before releasing GSX, we tested it with the current Trial versions of the following UK2000 sceneries:
EGLL
EGKK
EGLC
I also repeated the test again now after you report, and can't see anything like that, I'll try downloading EGCC to see if there's a difference.
In any case, if what you say here:
I presume this is a result of some technique gary Summons uses in his specially built scenery compiler.
I don't see how we could fix it from our end, our objects are all 100% compliant FSX .MDL files, there are no non-standard commands or other possibly unusual things.
Whilst you, hopefully, find a solution, could you please confirm that there's no limit on how many airports I can list to be GSX excluded? how long can that INI file line be? Usually I think the limit s something in the region of 256 characters, but it's going to take more than that ... unless it will access something like "EG??" for all EGxx airports?
I believe the limit should be higher, because even if it's a .ini file, we don't rely on the Windows API to read/write it but, since the whole program is written in Python, we use the standard Python library, which is OS-independent so, if there are limits, it could be different than the ones in the Windows API, and I thing multi-lines are also allowed and, it's possible that using some kind of usual Python magic, maybe it's already possible to put something like a regular expression to match a large number of ICAO codes, I'll confirm this after making some tests.