I'm not for sure on the Old Mac's I've never used them. I know many different one are not suppose to fit super tight around the upper part of the hoof. It would be like wearing a pair of really tight shoes.
Best test is to have the horse walk/trot around with them on. If they don't come flying off, the probably fit.
You can always call the Easy Care folks. They are very friendly and willing to help.
Kitten_Val if you don't like your Epics, you can convert them to BAREs. It is easy to change out the buckle-cable for the bungie that comes on the bares. Everytime I break a buckle or cable I convert and have converted almost all of my Epics over. The only difference will be that you still have the Epic Bottom. The BARES have a different traction pattern molded into the bottom.
The gloves have a Fit kit that you can order and try on your horses feet to decide what really fits. They come in half sizes. And we've seen horses that have different sizes on different feet. 0.5 on Right Front. 1.0 on Left Front etc.