It's offset 45mils to one side. You can get a spec with the exact dimensions from AMD's sight.
Regarding the issue of even water flow - remember that the channels you have are rectangular and the hose is circular
(hint - look at the formulas for the area of a circle versus a rectangle).
What Redleader was referring to regarding flow restriction is that water takes the path of least resistance. If the amount of flow through the 1/2" input can pass through say half your channels, then the other channels will have almost no, if any, flow.
To prevent this you need to balance the total flow of the not just the channels in comparison to the inlet, but balance the flow restriction seen between all 8 paths. The later not only involves the size of the channel, but also the length of the channel and the turns in them.