I would be really surprised if your GPU was broken up in to two separate circuits that each draw 75 watts.
My assumption is that the PCIe connector ground and 12v lines are electrically connected to the ground and 12v traces on the card edge connectors. If the PCIe cable has less resistance than going through the ATX12v connector and then through several inches of motherboard trace, then most of the current flowing to the video card is going to go through the PCIe cable which brings me back to sensing current there.
I didn't explicitly state that earlier but that was part of my reasoning.
The PCI-E connector and edge connectors are connected to the same ground, thus, in theory current will flow in the path of least resistance - through the PCI-E connector. Good observation!
But some current *does* flow through the bus connectors. I was doing some research and I found this: http://www.xbitlabs.com/articles/graphi ... html#sect0
Xbitlabs used a special setup to measure current draw on the PSU rails: 3.3v, 12v, and PCI-E 6 pin/8 pin. With a full load on Crucis Warhead, a 5750 draws only 1.4A on the 12v, and 3.3A on the PCI-E. But on a 5770 the 12V draws significantly more, 2.3A vs 3.9.
So if you calculate the CPU draw on the PicoPSU, in total there will be more current flowing to the PicoPSU then the 6 pin pci-e. Not by a great amount but certainly more.
What do you think about that? If it was your system and you wanted to prevent voltage drop, would you still put RS on the PCI-E side? Of course, I suppose there's also the additional Vdroop function on the motherboard itself, but still.