Serpent made Rollcenter Spacer SDX (SER500623)
The 2mm coated aluminum spacer fits beneath the differential and slots/keys toward chassis. You could spot 2 along with eachother to create 4mm spacer. The style is manufactured such technique your 2 spacers will even freeze position. With respect to the dishes use you may need to also spot out of the back stiffener. Increasing the rollcenter goes the differential greater aswell, creating more grip and steering, but less easy to drive.
