Catch 22.... 3" up, it will be forward of its normal position... but on bump travel it will be too far back.
What you actually want to do is make it longer and move the chassis mount forward.. this increases the radius of the arc and reduces the amount of wheelbase shift under articulation.. not a job for the faint hearted though.
I run Ironman bushes on the rear of Tigger, these are split at an agle around the chassis mount, this means that at rest, there is no pressure on the bush.
It means you can run straight radius arms, meaning that the forces from the axles are transferred up the arm in compression.