As long as your PCI-E are +12 and 4pin connector line, you are fine. There is no need to go buy another PSU.
Use 3 cables into one side and 2 cables to the other. It will run! (Trust me, I tested 5-cabel configuration and it mined at 180GH/S for hours)
Everything seems to work fine the way you describe. I put the 3 cables on the blade with the control board and the other 2 on the second. The miner runs fine and it hashes as advertised (180GH/s). The power cables are a bit hot to the touch, but not extremely. I'll monitor more closely for the first days, but I guess this is expected.
Thanks for your guide, it was very helpful. I was a bit surprised by the red led at first, but since everything is running fine I guess it is normal. Maybe it's worth mentioning in the guide...