The moment method solution for the scattering parameters of radiating slots in waveguides has recently been shown to be of sufficient accuracy to form the basis of a purely theoretical CAD synthesis package for slotted-waveguide array antennas. However, the efficient implementation of such a package can be considerably aided if some prior knowledge of the functional relationships between the slot scattering or admittance characteristics, and its dimensional parameters is available. These relationships have been discussed fully, in the literature, for all dimensional parameters with the exception, curiously, of the width parameter. The paper includes some theoretical and experimental observations of those width effects that are most relevant to CAD developments.