What does the big spinner have to do with choosing between a 18-6 or an 18-8 prop? For a maiden flight you may want as much thrust as you can get, that would be the 18-6. My OS 1.60 likes a 17-8 on my Ki-61, but I'm afraid it will rev a bit high on this plane that should be quite a bit faster. I'll run a 17-8 for maiden, but will likely run a 17-10 in the end. Even a 17" prop has plenty of blade area outside the spinner, not an issue.

On those elevator push rods, I may use the Y set up but I will but a connector between the elevator halves to stiffen things up a bit. I have not got to that part yet so I'm still looking into what I will do.