Thanks for the reply. What you describe is exactly what I did: new 300 F4 with TC 1.4. It makes SUCH a difference with birds in flight. Even Willets flying 40 mph have come out crisp and clean. I am not yet able to afford a gimble like you have, but am still able to get 50 to 75% of the flight shots presented to me by shorebirds and larger.
Did you start off using your 300 F4 without a gimble? How would you compare shooting with and without?
I doubt that I'll ever make it out to your corner of the world, but best wishes in all of your photo endeavors and beyond.