Ok, I finally got to measure the vGPU from the following points. I previously didn't contact the ground correctly so there wasn't any reading - my bad.

I've found out that without the jumper, the vGPU is 0.85v and 1.1v then 1.25v respectively. This sucks as I don't have 1.3v!!! I tried using 2 x PCI-E and 1 x PCI-E but it doesn't help in overclocking.

I need vGPU mod desperately, lol. Someone help?