What should be done to obtain a positive (plus) moment forward of the datum?

To obtain a positive moment forward of the datum, you should remove weight from the tail of the aircraft. In aircraft weight and balance, the moment is calculated as the product of weight and the distance from the datum, which is an established reference point on the aircraft.

A positive moment indicates that the aircraft's nose will be pushed upwards relative to its center of gravity, leading to a nose-heavy condition. If weight is added to the tail or redistributed toward the tail, it can lead to a negative moment, causing the nose to drop. Therefore, by removing weight from the tail, you effectively adjust the center of gravity forward, which creates a positive moment by shifting the moment arm such that the weight distribution is more favorable for stability and control in flight.

Adding weight or shifting weight midway would not achieve the goal of increasing the moment forward of the datum, as these actions might keep the center of gravity at or move it towards a position that is less favorable. Redistributing existing weight without removing any typically does not create the necessary positive moment forward of the datum unless it specifically redistributes towards the nose, which isn't guaranteed. Removing weight from the tail is the most straightforward method to ensure the moment becomes positive.