Oh my friends, with moving over to the completed section I missed your answers here, Sorry!
And what a great feedback, Thank you all!

Can you explain how you attached the stretchers and PE control horns?
The stretchers and the control horns has some pins, or I cut them from the fret, that there is a pin remaining.
I drill the a very small hole (Eduard says 0.3mm, buit I use even smaller drills found some time ago on ebay, e.g. 0.26x mm)
The I mount the horn with CA gel into the holes. Here in Germany I found some gel with the name "100% Sekundenkleber" means 100% CA, which works great.
Thanks again for all your nice words!
Cheers,
Frank