You can also try placing it bottom right and sizing by pixel count, increasing gradually until you reach your monitors full(ish) resolution
I haven’t tried full screen. But one of my configs looks like this :
                {
                        module: "iFrame",
                        position: "bottom_right",
                        header: "HOUSE STATISTICS",
                        config: {
                                url: "http://192.168.1.4:8123/mm-dash-right",
                                        width: "410px",
                                        height: "215px"
                }
                },
If I increase width, the iframe expands to the left. If I increase height, it expands up. Worth a shot.



