I just made a tag using the "tag by category". Its not as clean as the spot elevation but it does the trick. You have to choose the Fabrication Category under Load tags and symbols. If you dont have any to start with you need to load the family. Search through the browser US Imperial>Annotations>Mechanical>Duct. Load tags from there. Choose a tag, to use than select the duct. After highlight the tag, then click Edit Family at the top. Now, highlight the tag and click on edit label at the top. This will bring you to a window (pictured below) where you can change the parameters of the tag. I show the elevation tag that I made. Make sure to save as family, then load it into project.