I am on a Sierra MacPro with a Logitech Mouse and Apple trackpad.  On take-off and in the air I can't keep the plane from going into left and right turns.  If I'm turning to the left, using the smallest right adjustment I can make with the mouse,  I start turning right.  If I'm moving right and make the smallest mouse adjustment to the left I move past center and start turning left.  Have adjusted my mouse and trackpad to least sensitive in system preferences but it makes no difference.
I tried assigning option right arrow and option left arrows to the rudder and get the same thing.  If I'm turning right and I hit option left once I move past center and turn left.  If I'm turning left and hit option right once I move past center and start turning right.
Is there a way around this?  How do I keep the Cessna from turning?