Fits to the ${\overline{v}}_z$ data for Classical models. Each panel shows data for 10° sectors of the Galaxy, and plots the average v_z in 0.5 kpc bins, with associated uncertainties (statistical and systematic). The model fits with a single value of ϕ_w and ω_p are plotted in black, while those of the twisted model are in light blue. Overall both models provide reasonable fits, without major differences.