I think your report was very useful, this seems to confirm my idea it's not really the couatl.exe the problem, but something else.
Can you try it with the latest version (see the link in my previous message), without touching anything else ?
Got it working with version 2.0.0.2141 now!!!
The trick is installing Hawaii2 in OFFLINE MODE AFTER ANY SCENERY!
Otherwise it won't work... not even copying couatl folder in, afterwards...
So procedure:
Install ANY FSDT/FlightBeam scenery in OFFLINE...
Delete couatl-folder in FSX\fsdreamteam\couatl
Install Hawaii2 in OFFLINE! (<-- important step apparently... it won't work, if you install Hawaii2 intermediate and copy couatl-folder in afterwards!)
This method is working with version 2.0.0.2119
Copy couatl.exe (v2.0.0.2141) from Umberto's previous post, and overwrite in FSX\fsdreamteam\couatl
Hope it helps!