Rostock & Kossel hanging Extruder for soft filaments 1.75mm

13/01/2016: More tests done, many hours of uninterrupted printing later, I can say YAY!!!
Works well with PLA, ABS, NYLON, PVA, TPE, TPU, PET-G.

Hi everyone.
That's an extruder for flexible filaments and indeed works well with PLA, Nylon, ABS, PET, etc.
I found so little extruders with a really low mass. Nema17 are quite heavy and this makes the printer lose precision, speed and (many times) steps.

But how about suspend the extruder over the arms with some kind of elastic material to ma