Extracellular electrical recordings capture the spiking activity of multiple neurons in the vicinity of a probe. Typically, the features of interest in these recordings are action potentials and their timing. However, for planar probes that span tens or hundreds of neurons, it is possible to identify relative spatial locations of neurons. Such spatial information may be useful for reconstructing local network structure or for improving the quality of spike sorting. We propose a Bayesian modification of a dipole-based method for estimating neural positions from waveforms recorded on multi contact probes and investigate how sensitive it is to prior knowledge about the equivalent dipole sizes of neurons and the geometry of the recording probe. In addition, we determine the probe spacing and number of contacts which produce optimal localization accuracy within the class of planar, circularly symmetric contact configurations.