2x1 batons would be fine as long as you fix them through every joist above. Start around the outside of the room first making sure each baton is level with the lowest point in the existing ceiling, then fill in the middle at (I always use 400mm centers, but less is okay depending on board size) centers to suit. Use packers if the ceiling is not level.
When you fit the spots use a holesaw through both layers.
When you fit the spots use a holesaw through both layers.
