Not sure if you already built the rig with 5, but id suggest splitting to 2 rigs with 2-3 in each to avoid lots of headaches. 
What is this, one can easily put 5-6 GPUs per rig and benefit nothing from having double the amount of mobos, cpus, rams, psus, etc.
What kind of headaches have you faced when building 5-6 GPU rigs?
Powered risers.
In my experience, running 4+ cards without powered risers will cause the main power connecter on the MB to burn up, literally charred.
Remember each of those GPUS has the potential to pull an additional 75 watts through the PCI-Express bus (This is in addition to the external PCI-E power connectors). At four cards you are looking at a potential of 300 watts being pulled through the MB from the main MB power connector and through the PCI-Express bus. This is on top of the requirements of the CPU and chip set.
The solution to this is using powered riser in addition to the normal risers you will be using. (I hope one is not trying to run 4+ cards directly on the MB, you would never be able to dissipate the heat.)
I used run my rigs with 4 cards w/ a powered riser, but for some reason the powered risers seemed to start causing their own issues. It eventually became easier to just run three cards per rig and save a lot of headaches.
Just my experience and 2 cents...Take it or leave it.
If those temps are reading correctly, you're going to burn the 1st and 3rd card out quickly. Dust them out, fix the airflow, and get some fans directly on them ASAP.
