I used fontself for illustrator to create my font with 4 different styles. The extension supports only few styles (Regular, Bold, etc.). But there is an option to select other in the styles and type our own style name. My font contains regular, medium, bold and black. After I install them, they show up as installed but medium and black behave as regular. The ones that have my own style name don’t install properly and are not usable on my windows machine. But works well on my mac.