Spider coupling with Sugru insert mold

This is a derivative of MiseryBot's excellent spider coupling http://www.thingiverse.com/thing:7678

I basically modified few values to have it fit the 8mm diameter of my trapezoidal spindles - the original thing was adjusted to fit the common M8 threaded rods whose diameter is slightly smaller than 8mm. Additionally I corrected the M3 nut trap sizes since they were little too small to match ISO 4032 nuts.

Finally I used the insert-positive to quickly make a simple, but great working mold f