In Part I we developed a fingering function for Fayers macroscopic model which gives acceptable characteristics for fractional flow, average concentration as a function of distance, and total mobility, when compared to high-resolution simulations for non-gravity flows. In Part II, we examine the influence of gravity on rectilinear flows, both for cases where gravity is either stabilizing or destabilizing. The Todd and Longstaff model is also analysed for these gravity cases and shown to have very good characteristics for the stabilizing direction, but it shows some deficiencies for the destabilizing gravity direction. The new Fayers fingering function clearly performs better for the second class of gravity cases. The optimum parameters for both the Todd and Longstaff and Fayers models vary with the gravity number, and expressions axe given for these quantities.