You have to find "perfect vertical". For your Knife, that's just a tad on it's back.

If you try descending a little while hovering, that will definitely help it roll. It's harder to hold the tail under the prop, but it will roll.

If there is wind, you have to be going with the wind. Can't hold it stationary if there is wind and have a torque roll. Has to be NO wind relative to the airplane.

Try an 11.5x4...

Kick in some aileron to cheat.

The real solution is more torque...That means a 4 stroke like a Saito .72 or YS .63.