Let's try the long refractors stopped down a bit. I wasn't quite consistent here, and forgot to shoot the Zuiko 600 stopped down without the teleconverter.
And in detail:
The Tamron is STILL a dog, and the Zuiko 300/4.5 still beats it easily, although the Tamron again cleans up nicely with the teleconverters — the opposite of what we're always told.
What's really interesting is that the Zuiko 600 doesn't look any better at ƒ11 than it did wide open. I'm liking this lens more and more!