Vuforia - aligning AR view of a room [model] with the ACTUAL view of the room [actual], as seen via device camera [ipad-mini]

i am trying to use vuforia as a tool to display the design proposal for a room interior as an overlay on the actual view of the room as seen via the camera... but the AR display is different from the actual dimensions... where the display begins attached to the target it is alright but the further away from the target the variance of dimensions between the AR display and the actual dimensions of the room begins to become more apparent....specially if the walls are in curvilinear shape.... a test project can be viewed at: https://drive.google.com/folderview?id=0B1W8dDSQl78AMVdQWXNoaVQ5V1E&usp=sharing and the pics of the results are below: i have an idea that this issue may be resolvable via projection matrix, but need help in the specifics