Just done this kind of mod to my 160w pico. 6pin male to 8pin EPS (not pcie) for mobo with a pigtail for power the pico. All off a single 6pin pcie from my server psu breakout board. Only 7inches long so nice and compact for my small rig.
They sure make things nice don't they? Of course am using EPS connector for cpu. I can shorten up the power leads if people want them shorter. I need them long for my cases though.