Thanks Rick!
Still somewhat paranoid about misaligning the engine and/or Spandaus...I check about all I can check.
Found (part of?) the problem!
The frame in between the magazines and (missing) fuel tank is too small.
When you glue it to one side...there will be a gap on the other side...and the magazines will be off centre.
Easy to overlook...easy to fix also. A 0,25mm thick strip of Evergreen wrapped around the frame and it will fit like a glove.

Furthermore...
Opened the frame, adjusted the floor board and pit upgrades.
The NZ D.II replica photo's from James Fahey (Jamo) and the Brad Cancian Roden 1/32 D.III photo's are very helpful.
Merry Christmas!
Robin