In this work, an extension of the Method of Moments with Interpolative Closure (MOMIC) is presented. In many flames, the soot Particle Size Distribution Function (PSDF) is composed of both small spherical particles and large aggregates. An appropriate respresentation of the bimodality of the PSDF is required to accurately predict soot volume fraction, number density, and aggregate properties. It will be shown that, unlike other methods such as Direct Simulation Monte Carlo (DSMC), MOMIC does not properly account for small soot particles in these flames. In this extension, an additional transport equation is solved to account for the influence of the small soot particles. The source terms for this equation are derived in the same manner as for the Direct Quadrature Method of Moments (DQMOM). With the extension, MOMIC is shown to predict soot volume and number density very accurately compared to DSMC. In addition, aggregate properties such as the diameter of the primary particles and the size of the aggregates are better predicted. The extended method is also shown to accurately predict experimental measurements.