To minimize the effect of permeability variations of tipping and plug wrap paper on the degree of filter ventilation and consequently on the smoke yields, a mathematical model for the flow through a layered structure of perforated tipping paper and porous plug wrap paper was derived. The output of the model was compared to experimental data and a very good agreement was found. A statistical investigation revealed that measured permeability values of tipping and plug wrap papers are normally distributed. Furthermore, it was shown that the statistical distribution of the total permeability of the layered structure cannot be distinguished from a normal distribution at reasonable levels of statistical significance. Based on these investigations and on the mathematical model, expressions for the expected value and the coefficient of variation of the total permeability were derived. It was shown that in spite of the non-linear model the difference between the exact expected total permeability and a simple estimate calculated from the expected permeabilities of tipping and plug wrap is sufficiently small, such that for all practical purposes this estimate can be used. The coefficient of variation of the total permeability was then minimized. The solution of this optimisation problem delivered practically applicable design rules for the permeabilities of tipping and plug wrap papers. It was shown that the minimal coefficient of variation of the total permeability is lower than the coefficient of variation of the permeability of tipping and plug wrap paper. Typically an optimal design can be achieved by choosing the tipping paper permeability between 10% and 50% higher than the total permeability. A simple example demonstrated the usefulness of this approach.