Other considerations of macro flash is the subject matter. For instance, living critters can be damaged by flash so close.  I choose not to use flash on living things with eyes in a macro setting.

I have used a ring flash  capable of both left and right flash level control.  Have one side flash more intense than the other  to help achieve a desired contrast ratio, meaning essentially  the shadow.  I imagine you know about that. My comment is on the ring flash:  The left and right, up and down, however you do it...spacing does not seem adequate to get a good contrast.  I have almost in all photos found natural light including natural light with a reflector to do better in gaining a pleasing contrast effect in a macro shot.  Perhaps I am simply not experienced enough to do better but the ring flash with level control for two sides has disappointed me in the field..

Best wishes in getting the lighting you need working to suit you.        TomDart.