Couatl/GSX don't have anything to do with FSX OOMs.
Couatl.exe, being a separate .EXE, has its own separate VAS space and the whole GSX code runs entirely inside it so, whatever thing is causing OOMs, you can be sure it doesn't have anything to do with GSX. Especially if the crash happens while flying, when you cannot even account for the (small) additional memory required by the objects created by GSX at the parking, when you use it.