This Tutorial is for Nodekit version 0.7.5. In newer versions, the drawing area is automatically resized and fitted to the current screen resolution.
Tutorial for Nodekit Version 0.7.3 and 0.7.4

In some cases the automatic adjustment of the drawing area fails and drawing is constricted to a smaller rectangle than the screen size. Here's how to fix this:

Step 1 - If you're in fullscreen Tagtool mode, press alt-f to change to the Nodekit view. In the Tagtool Patch, look for the CameraFitToContent Node that is connected to the Display Node (eg Display2:1). It's located in the upper part of the Tagtool patch - indicated by a comment box (“TABLET AREA MAPPING FIX”)

Step 2 - Change the “Norm” Parameter in the CameraFitToContentNode. Lower values mean bigger drawing area. Press 'Enter' to commit value. It works the same way as in previous versions, but got some comment node next to it showing some brief explanations and it´s also a little bit easier to find the “CameraFitToContent Node” in the Tagtool patch.

Example) My Norm value was '27' before I lowered it to '20'. Drawing size now matches screen size. Screen res for me is 1024×768 (shown in Display 2:1 node).