@Jan_erik_Halvorsen aahh that one. Saw that nice
@Mark_Rehorst To this
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@Mark_Rehorst
Yes its printed in ABS and you could make a 250mm loop if you wanted 
@Mark_Rehorst
Also other than cablechains the wires are free to bend where they want. Cabledefekts are less likely
I did light drive motors on my own belt driven duallie, but I had a reduction of 3.75:1, making up for the low torque. My carriage totaled about 600g. Which is still considerable mass but I’d found it wasn’t terribly lot more than many direct drive single extruders at the time.
My 2 into 1 extruder weights 450g complete with everything and my single extruder 238g without fan. the fan is 20mm and weights 7g. Print quality has increased with the new extruders probably because of 0.9 degree stepper and 4-1 gearing which gives 2500steps / mm. I can also print at higher speed without sacrificing print quality.
Your dual extruder concept looks similar to mine, I fed into E3D cyclops rather than two separate hot ends (no drooling) : http://www.thingiverse.com/thing:852748
2 into 1 works really well except certain colors where you can get a little color mixing and I would like to have better control of the purge tower speed in S3D to shorten the print time.
@Jan_erik_Halvorsen thanks for the info. Thats about what my will weigh. Must work out. My Y carriage is way heavier.