Finally I have solved my problems with the quad turning left and right without touching yaw stick... Don't know if the key is latest ACM versions or the fact that I mount the APM/IMU over foam to reduce vibrations... in any case, now I can abuse of pitch/roll sticks and yaw is rock steady!
Unfortunately, I have a new problem :(
I can yaw to the right (although very, very lazy) and when I release the stick the quad stops the turn but when I yaw to the left (and release the stick) the quad spins but it does not stop!!
I tried with YAW_OPTION = 0 and 1, and also STAB_YAW_P between 0.3 - 0.7 without success.
I attach the log, where you can see four attempts to yaw to the right (the first two were not able to produce a real movement), a first yaw to the left that worked ok and a second yaw to the left that produces a not stop spin (more than 360º) until I have to take off!
Hope that someone can have a look at the log!