After the 3 day in town delivery UPS finally get you 
May I can try helping
May I can try helping
Dear Martin,
...
So i tried your boards with hexmine in win7, tried all the combinations got 42gh with one board, 77ghs with two, 91gh with three, 101gh with foor
it's little wired why its slowing down when you add another device, it's suppose to be additional.
...
Thanks
My first thought from reading that is that your boards are being starved of power as you connect more. Have you tried running each one singularly to make sure they perform okay. Then try them together on different power sources (if you have two or more PSU's available), so you've got PSU one to board one, and PSU two to board two etc, and let us know the results. What settings are you using in Hexminer, can you post a screenshot?
It's seems power issue but 2 of 500w psu connecting 4 boards only.