Again, its not usable at 3 FPS
I agree, surely it's not. So, I guess many others would have reported it, if this was a common issue.
It only happens with the PMDG 747
That's why I tested it with exactly the same version as you reported. Yes, there's a slight fps drop, but it's surely acceptable, since you are not flying.
All other aircraft at that airport has no FPS drop using GSX.
I was sure of that. But I'm not putting any blame on the PMDG. Yes, it's a demanding airplane, but it works normally at KSDF here, and nobody reported it before.
SO only the 747 has issues with GSX at KSDF. It doesn't make sense to me, the 747 works fine with GSX at all other airports except KSDF.
It doesn't make much sense because, if the PMDG 747 doesn't work well at KSDF, but other airplanes do, doesn't fit with the fact it works well at other airports, but not at KSDF.
When you say "other airports", do you mean also other FSDT airports too ?
I have reinstalled & done all live updates
Have you done the same with the PMDG 747 ? Do you have the most current version ?