For those having issues using both their mouse and XBox Controller after SU5 please try the following solution. This will reset your deadzones and thus allow you to once again use your gamepad and mouse to manipulate your cockpit, external, and showcase camera yaw & pitch. There will still be a white-dot in the middle of your screen where your gamepad target is but it really is not that bad and moving your mouse will remove this target.
Hope this helps 
Main Menus > Options > Controller Options > Sensitivity > Reset all 6 axis