It has not been my experience that they are necessary: The atmospheric condensation forms on the valve as an ice ball, not as liquid condensate that drips off. The potential for dripping would be when you are taking the system down and everything warms up to ambient. As the ice ball melts, it would have to drip. Floor drains seem to take care of that eventuality, if the valve is indoors. Outdoors: it drips on the ground and soaks in to the soil or evaporates from the pavement.
I believe that collar drip plates are often used for terminating the lagging or, more specifically, the casing for the lagging around cold pipes that the valve is in. Therefore the size would be dictated by the requirements of the lagging rather than by the valve size per se. I would suggest that you talk to your client. I have made the same size valve with differing sizes of drip plates for this very reason.
If there is no lagging then I agree with Jim; an exta inconvenience that adds nothing to the performance of the valve.
