Easiest way would probably be to define the:
E1, E2, E3 (Youngs moduli in global X,Y,Z direction)
Nu12, Nu13, Nu23 (Poisson's ratio in global X,Y,Z direction)
G12, G13, G23 (Shear moduli in global X,Y,Z direction)?
when I have vertical/horizontal stiffness and the W*L*H of the rubber bricks?