You need to set this variable -
IMG_RENDER N P/L/A Opacity multiplier to render on top of raster. If feature has an alpha of 128 (50%) and Opacity Multiplier is 128 (50%), the resulting Opacity for the feature on top of raster will be around 25%. For points and lines, Min (0), Max (255), Default (255). For areas, Min (-1), Max (255), Default (0). -1 will render only the border for area features.
To specify areas, you also need to export as At5 version 13+ or you need to select "Auto Create XML" in "Advanced Options->Vector Options" and copy that At5.xml file to the card.