Usually after painting in dark color, the contact wire becomes visually thinner. For Z, it is possible to solder a contact wire from thinner wire, than at Marklin. And current collectors of locomotives to fix, that they didn't concern a wire. Z very small scale, there all too gentle. There will be no friction and load of a contact wire - won't be problems with a thin wire.
//This forum mangles the Umlauts, sorry!// -it isn't terrible))) I am not German, I Russian. In my language the Umlauts isn't present.