Upper QPO frequency predicted by the Ep and RP0 model plotted for a = 0 and tori whose thickness ranges from an infinitely slender torus (β = 0, black line) through a torus with a cusp (β = β_cusp, red line) to a torus whose outer edge extends to infinity (β_eff = 1, dotted red line). The blue arrows indicate the spread of the resonant frequency implied by the allowed spread of β for each model and the 3 : 2 QPO frequency ratio.