I use 2X6X14 pressure treated boards in conjunction with Levler Blocks. I have found that the Weight of the Class C often pushes the blocks into the ground, do I use the boards and stack the Levler Blocks ontop of the boards if needed.
I have a rear portable stabalizer I purchased at Campers World which I put under a rear horizontal frame which my Reese hitch is attached to. This is under the rear bed and eliminates the rocking behind the rear axle. I don't notice much rocking or movements in the middle of the coach in between the axles.