The following pictures dictate how the end of the dash pad was installed at the factory and how we install them today.
We cut the minimum away so that we can cover the end without leaving any material around the cap in view. The original pads were just cut off as shown in the picture of the original pad below (this is my personal 90k mile car original dash pad).
Original Dash Pad from the same car showing how the factory did the end of the dash pad. It was just hacked off and covered by the cap.