A new cross-linking algorithm, NETSIM, is described which enables the study of continuously spatially distributed (off-lattice) polymer networks and reveals some topological features possibly associated with the enhanced mechanical properties seen in certain bimodal elastomer networks. These features art;identified based on trends in their occurrence at various mole fraction and molecular weight combinations and comparison with data found in the literature. A length scale, the linear cross-link spacing, is defined which is associated with these features, to characterize optimal bimodal mixture combinations. NETSIM is unique among cross-linking algorithms in that it employs nearest-neighbor periodic boundary conditions to eliminate edge effects and reduce the necessary computational size from over 10000 primary chains to roughly 1000. Computational size reduction eliminates the need for subdivision of the cell, a possible source of bias in results reported in previous research. This work also offers, for the first time, computationally determined gel fi action and extent of reaction calculations for various bimodal mixture compositions. For verification, NETSIM results on unimodal systems are compared to previous unimodal simulations with good agreement.