Compounders combine insoluble sulfur, accelerators, bonding/hardening resins and fillers to develop high modulus compounds useful as structural components in plied rubber articles such as tires, hoses and other industrial rubber products. Networks, as formed from bonding/hardening resins, suffer network destruction due to mechanical deformation even at small strains. Accumulated damage resulting from severe dynamic service can lead to continually softer and increasingly hysteretic components. Increasing filler to enhance modulus, such as carbon black or silica, increases compound weight resulting in less energy-efficient products (heavier weight, higher rolling resistance). Sulfur networks are known to be highly durable and self-healing. Compounding with high levels of conventional insoluble sulfur leads to processing limitations both in terms of sulfur levels and processing rates due to the polymeric sulfur thermal instability. This paper will discuss performance optimization in high modulus compounds using cyclododecasulfur, C-S12, a novel insoluble sulfur, which is unconstrained by conventional rubber processing temperature limitations. Increased sulfur and filler networks based on highly loaded cyclododecasulfur and self-interacting carbon black demonstrate improved dimensional, lower heat buildup and improved mechanical durability compared to dual networks based on non-self-interacting carbon and sulfur cure systems.