Today I mounted the remaining two motors. That wasn't too hard I have one recommendation though if using brushless outrunners: The outer diameter shouldn't exceed 18mm if the intention is to make a direct drive.
I also started mounting the rudders. No pictures yet. Instead I would like to present the motor mounts I made. See the one in the pictures below.
The motor installation was also tested today. All motors still works and will turn the propellers. Further I secured the propellers to the shafts using green LocTite. Green LocTite should be virtually impossible to remove. If removal should be needed, heating should be the way.
Today I got the white balance right