I needed 2 meters cable so… my first idea is to make it easy… cut the originale grove cable and weld in the middle another cable (as Wio say) but the simpliest idea seems to be not so good.
The device will not work, I’ve tryed with different kind of cable, from the flat to the silicon shielded cable… no matter what kind of cable you use! still not work, every communication protocol that I try to use from the I2C to 1-wire still have bad final.
I start to think there’s some kind of magic in the groove cable! 
Maybe exist a valid reason because the max length of commercial cable is 50cm!
Do you have any experience about this?