Fits to the ${\overline{v}}_z$ data for the v_R term models. As in Fig. 2, 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). Note that the uncertainties are larger here because we include uncertainties propagated from the v_R uncertainties. The models with a single value of ϕ_w and ω_p are plotted in orange, while those of the twisted models are in green. Both models provided reasonable fits, but note in particular that model ${\overline{v}}_z$ values are all around zero at larger R.