Has anyone used both the 6" and 3" together in a wall. I am bidding a job, 14' by 14' patio with radiused corners. The ancestral knee wall will border the entire patio terminating with pillars at one side for the entrance and terminating on either side of a precast fireplace on the opposite side. My concern is at the termination points and the fact that the block is hollow reducing splitting capability. Thanks for your thoughts.