Dear Jochen,
awesome work. Congratulation to this tiny and well done model in a model ;-)
Just two words. Min. one cable you could fix on the top of the helmet.
I´ve seen it on an older helmet of Frank Biela. The cable was fixed by Velcro tape. After entering the seat and fixing the seat belt, they took then the end of the cable from the top of the helmet to put it in the socket.
And now I´m waiting for progress of the Porsche. :-)
Tschöö
Dirk