Ford, where do you live. Greenheart and Tatabu sound exotic. Hurricane winds point to the South. NC.
Is the building an open ceiling or is there a floor going in at the eve line? 20' sounds like a stretch, maybe a third truss in the center. Dragon beams at the corners, for the hips? Can you get 10x10x38' from the species you listed? Purlins? English Tying joint? Back to the open ceiling, if there is no floor or ceiling then there is no call for joinery on the tie and so it could be sized smaller if needed, due to the size of the logs. A large timber just adds weight to the truss. 10x10 aren't all that big. Lets see if anyone else has some comments.
I am just starting a 20' truss system tomorrow morning, using 9x9's, mostly because they sawed out nicely. I even had an extra which I hope I don't need. Tim