Thanks for the quick response, i understand tuning the hashing power is not a simple task, it was just a brain storming suggestion.

From my personal experience for the last three days, the low difficulty doesn't fully mitigate the high orphan rate (specially for WDC), my profitability always drops down during these periods.

h2odysee,

I am not currently a member of your pool, i just found about it recently but i certainly would love to, i think it is a great idea and a major relief to miners by simplifying the economic decisions.

I have been reading through the thread to know more about the pool and noticed the profitability hit that you have been experiencing for the last three days and i can relate to that in a different way.

I constantly mine several coins of interest through out the day, for the last few days some coins (specifically WDC & DGC) have been going through a daily difficulty fluctuation cycle, where the difficulty plummets for 3-5 hours and then goes up again and the next day plummets again, these difficulty variations can be quite large (from 3.x or 4.x to 0.x).
For the last 3 days, during the low difficulty period, there have been above average miners (either through your pool, multipool, or even CGwatcher) suddenly switching to the coin, the sudden increase of the total network hash goes too high for that low difficulty that the orphan rate jumps to extreme values (60% - 70% in case of WDC). Although on paper the coin should be highly profitable, in reality sometimes it becomes less profitable than its normal value.

I am not sure what could be the solution to this situation, cause it seams to affect everyone either on your pool or the ones mining at the coin dedicated pool, i believe everyone will be suffering from the high orphan rate. Maybe tuning the amount of hashing power directed to these fast coins during their low difficulty might help.

Meanwhile i will be pointing one of my Rigs to your pool and see how it goes.
Good luck.

So i guess its time for me to bounce the question back to you, "Do you feel lucky?"   just kidding.

The only troubling part is about the card's memory drawing its power from the PCIe solt, that what makes all the difference between the Bitcoin and Litecoin mining. So i guess it will come down to your Thread Concurrency setting, too high TC will result in more memory used hence more power draw.
You can always check the mobo and power connectors to see if it is running hot as they described, not sure how we can do that effectivly with all the head blowing from the cards

No One can claim to be that lucky 
check this post, have some figures on the PCIe slot current but for bitcoin mining
https://bitcointalk.org/index.php?topic=199706.msg2082941#msg2082941

Thanks for the quick reply.
I am still not buying the need for powered riser with the 7970s, moderately OCed at stock voltage (1.17x v) each card burns approx 270W-280W (at wall socket measurement), since each card is feed with dual 8-pin PCIe power, that's 300W total which makes power draw from the mobo a minimal amount unless the card by design prefers to draw from the mobo than the PCIe power input.

Sophokles,
Excellent Setup, neat and tidy very well designed. Did you try the 13.5 Beta drivers, they are very stable for me even better than 13.4

Back to the issue of the PCI-e riser cables, as i can understand you are currently using 1x risers (non powered) for all five GPUs, it that correct?
i have been reading tons about the subject and there is lots of conflicting views out there, so i would prefer the experience of a working setup.

What PSU you are using that provides 10 x 8 PCIe power connectors?