RE: Prop for TT.61 on Extra 300
No 3D???!!!!!!!! You are in the wrong forum! Heheehehee ...
The TT61 will not take the 14x6 well ... I ran mine very well on 12x6 and 12x8 on a Black Horse Extra 300 60, you may be able to get away with the 13x6. I have run even a 15x4W on her before but that was on a Harrier 3D 90.
As for your choice of engine, it will be marginal or decent only ... you are better off with at least something that performs well like an OS91FX, best is if you can run a 108 2C. You will get good, not 3D, performance with a TT61 on a plane of less than 7.5 lbs.