Top left: base model for physical disc simulations. We scale this model for each semi-major axis case. Thermal emission from the far side of the disc is seen in the right side of the frame and forward scattered light in the top left. Top right: 30 mas case. Here we see the double lobe structure caused by the far side of the inner disc wall. Bottom left: 60 mas case. The arc of the far side of the disc wall is clearly seen but is comparable in strength to the artefacts within the frame and so would be difficult to identify in practice. Bottom right: 90 mas case. The forward scattered component is now the dominant feature within the frame. It forms a single lobe owing to the greater concentration of flux in the centre of the arc than in the thermal emission from the opposite side of the disc wall.