Really have to agree with him about the .61 on a twist. I had a .52 magnum on one and it was overpowered, using either an APC 12X4 or 12.25X3.75 APC wide prop. A good running ball bearing .46 engine is more than enough power for this airplane, expecially here in Texas. If you think you need more power, then invest in a Tower .46 muffler for your TT, OS, or Magnum .46 sized engine. The plane is allot of fun, easy to see with a good color scheme, but isn't a good choice for hovering, since it is so close coupled.
ORIGINAL: tIANci
I ran a 15x4W on my TT61 2C. It was okay, experimented it on my Harrier 90. A 13x4W is very little prop for the 61 2C for 3D, maybe a 14x4W as a minimum.
On another note, it is not worth it to fly the Twist with a 61 2C. The extra weight of the engine will increase the wing loading by heck of a lot. The increase in weight is more than the increase in performance. I tried this combo on quite a new planes. Best engine is something like the Twist is a SA82 turning a 14x4W.