How do you create medals that look and feel like the "right" size? It all starts with your design. The amount of detail in your art usually is what drives the sizing decision. This is why it's an advantage to let your supplier of choice view the design before getting it approved by your event committee or board of directors. We can tell you of a number of instances where a professional designer has submitted art that creates manufacturing issues and they don't turn out the way they wanted. We love getting completed designs, but be prepared for us to suggest edits that are a result of stamping or casting limitations.
The vast majority of submitted art is drawn at three times scale on a letter sized document. It's also common for designers to zoom in and out on their screens in order to see details and overlook the fact that you are zooming in on some very small details that might be illegible on your finished medal.
Remember we are stamping the bases out of metal. It's totally different than designing a logo for a website. If you print out your pin at actual size, you'll notice issues with
Note that we usually make the text on medals UPPERCASE. We typically space the text out with a spacing of 80-100 to allow space for the letters. This is especially important if you are getting antique finishes. If the letters are too close together you can't read the text because the raised area isn't large enough for the buffing wheel to remove the antique.
Learning to design for medals takes a long time. You have to completely reinvent how you design because you are using a base metal in your design in addition to enamel and electroplating. This video does a deep dive into how to use base metal in your designs.