Adding trusses in with archipack

Hi

I've recently started using Blender with the Archipack addon and noticed an issue with creating trusses. Trusses lie on top of walls and bear the weight of the floor above, so why oh why when you create one on top of an existing wall does it point skyward? I realise that it can be rotated back to the horizontal but this seems rather silly when surely you can code it to land horizontally on top of the chosen wall. Thanks in anticipation. Tim