"We offer new support options and therefor the forums are now in read-only mode! Please check out our Support Center for more information." - Vuforia Engine Team

Where is the target center?

Is the center of the target defined by the geometric center of a bounding rectangle imposed on the target, or is it defined statistically based on the distribution of feature points in the target?

It should be pretty easy to translate your rendered content in code, once you come up with the correct X, Y offsets. Measure your target and find the point you want to be the "world center." Find the X, Y offsets from the center of the target, percents will probably be most useful here.