I was unable to hold the plane hovering more than a few seconds because it was very unstable and started immediately torque rolling. With a lot of effort I could resist up to two or three torque rolls before the plane drops.
After I modified the rudder making it taller and move the c.g. back a bit ,the plane performs very differently. Now it's very easy to hover but it does not torque roll at all. I can hold a hover for as long as i want to with no effort.
Maybe some of the experts in this forum could explain this torque roll effect.