ORIGINAL: countilaw
In the 70s and 80s, we used torque rods in a pattern plane with a screaming 61 on a tuned pipe. Didn't have any trouble with them then. You really don't get any flex with a 1/8 " piano wire.
But sometimes it's easier to use a servo in each wing panel.
Whatever floats your boat.
Frank
The length of the tork rod is critical to whether one gets torsional flex of not. On classic pattern models with strip ailerons, the tork rod run was very short so 1/8" piano wire worked fine.
If the tork rod was much longer, 10" long for example, 1/8" piano would not be stiff enough.
Plug in wings make tork rods impractical.