A kinetic Monte Carlo modeling study is presented for precursor polymer formation via the sulfinyl precursor route. The premonomer, 1-(chloromethyl)-4-[(n-octylsulfinyl)methyl]benzene, is subjected to a NatBuO induced 1,6-elimination in sBuOH yielding the actual p-quinodimethane monomer that leads, via a radical polymerization, to the precursor polymer. The kinetic Monte Carlo model is able to predict the experimental trends in yield, mass averaged molar mass and structural defect content. The effect of radical recombination and cyclization is modeled and found to be negligible. The effect of the initial base and premonomer concentration on the polymer properties is investigated. Simulation results indicate a maximum in the polymer yield and chain length for initial [base]/[premonomer] = 1 and that the molecular properties of the precursor polymers can be varied by as much as 50% by an appropriate choice of initial [base]/[premonomer]. The kinetic Monte Carlo model is used to determine reaction conditions to achieve targeted polymer yields, chain lengths and structural defect contents.