I got the MDC speedometer. It is fantastic but for you to do what I did would be a lot of work for what I see as little gain. I’ve used the JMRI speed table for each of my 25 locos and start with the lowest speed the loco with move at setting 1 and then limit the top end of all to 50mph. With 28 steps, I set up each step at 5, 10, 15, 20 and 25 (ignoring the ones above 25). That way when I’m running at any setting, I can just double it for a realistic mph. It is a tedious task but well worth it since I plan on running many different consists.