In an earlier work we described a laboratory-based experimental series that demonstrated the transition from velocity-shear-driven ion cyclotron wave heating to ion Joule heating as a function of ion-neutral collision frequency. As part of this effort, we demonstrated the ability to control the magnitude and direction of the electric field (or the sign of potential change) in space in a simulated ionospheric environment. In the results presented here we have calculated the electric field by differentiation of a fit to the potential profile and have used the full width at half maximum of this field as a marker for the size of the region. In the case of the ion temperature measurements, which are derived from energy analyzer data by conventional techniques, we demonstrate increased ion temperature consistent with increasing electric field region length. We also have been able to demonstrate a peak in the ion temperature as a function of collision frequency and the Joule heating rate. The data suggest that for approximately constant pressure and electric field strength, the normalized ion temperature increase will be limited for a given scale size. Finally, we argue that these observations are consistent with the notion of a limit to ion heating based on a comparison of the scale length of the region to the mean free path for ion-neutral collisions.