hi  in 24 years of building -i have never put any -right thrust into my aircraft-  just feel it is more efficient if the engine is at  zero degress with the stab and wing at zero degrees  - my instructor building for another 30 years felt the samemy planes fly unrealjust my  2 cents-i have been told that some down thrust will help fly a plane invertedthat is tail heavy-which is required for 3 D flying -but have never done that to datethe   friend that told me that- is resposible for inventing three -3D manouvers YURI HIGUCHI