you don't have to, and it's not about the DBW, maybe the author removed the turret, I remember that there was a problem with it, What I can tekk you is that SAS Epervier made a 4.09 copy of this mod with a working turret, and so download that put it in to the DBW folder and right after that put the DIFF FM mod INTO the HE-111H20's folder, this technics works with many 4.09 aircrafts, like the vickers wellington.
Good luck!