Your OS40 will be too weak to 3D. I had a 46ax and it worked but was a bit lacking in the pullout department. A .46 to say a webra 50 or OS 50 are great 2-strokes or any of the .63-.82 4-strokes would really get te job done. Since you need 2 more servos take a look at the Hitec HS-635hb servos. I had them all the way around on mine and loved them.

Dave