Thank you for your kind and constructive comments!
Certainly you are right about the turnbuckles (macro photos are merciless...), but my attempts stretching Q-tips all went wrong ( must find other cotton buds).
Xan, you can fix the roundels in toto, before they have set finally you can make some cuts with a scalpel beside the ribs, so there will be no difficulties. I used Micro Sol and Set.
Highest regards,
Jörg