Mapping X and Z values from the Kinect to X and Y values to a projection wall

I’m working on a project that is basically an interactive wall in a very limited space. Therefore I’m forced to have the Kinect be on top of the projection wall and check within certain threshold when a finger enters that area. I was able to not only manipulate the depth threshold which is already solved in Theo’s Kinect example but create one for the X and Y of the image, that way I only have in that threshold the wall from top to bottom:

As you can see, there are two elements on the screen, but only the center element gets tracked displaying only one blob, so far so good. Also the Kinect does the correction to return the same Z value regardless of the position of my X.

Now the problem is that when I want to map the Z value to a Y value of the projection this is what I get:

As you can see on the red box which is a mockup of my projection wall. That was an element moving from the top left to bottom left but because the lens has an aperture angle, a straight line from top left to bottom left is seeing as a curvy line.

So before I jump into some weird math, is there any addon or example that has taken this into account when using the Kinect in this fashion? Any suggestions are more than welcome, hope everything makes sense.

Thanks in advance