Fantastic, one-of-a-kind extension! I looked for a subtitle player and this add-on was the most flexible one. I mostly use it as a layer and this is a feature other addons are lacking. Full screen by definition brings the video to the foreground, so no subtitles on top, there is no workaround yet within FF (still I can press F11 and zoom the page in to make video almost fullscreen).
I wish I could try new v2, but I press the button and the popup menu is blank. Maybe it's my old browser, FF 47.0.2, I think it's not any other extension. Anyway, I give the dev 5 stars because it's awesome! Thanks!