The smaller part should be able to print without supports. for the bigger part i used the "tree" support structure and it worked out fine.

I tested it only on the back side of the car at a speed up to 240 kph and it did not fall off.

Inspired by: "TWIST 'N' FIX KENNZEICHENHALTER V3 ZUM SCHRAUBEN" https://3d-kennzeichen.de/zubehoer/twist-n-fix-kennzeichenhalter-v3-zum-schrauben

I shall assume no liability for damages because of unsuitability for the purpose of use./ Ich übernehmen keine Haftung für Schäden wegen einer Untauglichkeit für den Verwendungszweck.