Stefan, I have left the pins. On the other hand I had to drill the holes in one side of the fuselage, as they were not present there. I have indeed noticed, that the pins were not symmetric between both lower wings, so I drilled the holes slightly assymetrically, too. Thus the wings are correctly positioned and the joints should be strong enough. To make sure I have filled the upper side of the joints with a liquid CA glue.
Gregory, many thanks, you are very kind, as usual.