[Therion] How can I make bitmaps overlapping in a transparent way ?

Hello, For Fuchslabyrinth cave, we're using primarily morphed bitmaps. With the default thconfig settings, at areas where bitmaps overlap, one of them is "half-transparent". (See attached image) I played with the "opaque" parameter, but the results are not what we want: opaque = 100: overlap area shows one of two bitmaps only. opaque = 0: All bitmaps vanish completely. opaque = 10: either bitmaps are drawn in extremely light colour, hardly visible. What we need is full visibility (100%) of either bitmap, regardless whether they overlap or not. Any hints how to achieve this ? If this is not possible, is there a way to control which bitmap is on top ? Regards, Michael