Yes that is a good idea Harvey, especially useful when engraving something like a gallery tray (you may not have these) silver trays with a rolled pattern and an oval clear patch in the centre. Getting it lined up can be tricky.
Another way, especially if the text is long, i.e. 5 or 6 minutes, is to save the layout, then delete the text, put a single letter in each corner of the top and bottom line, then set the machine running. You can see the four corners "engrave" and judge its position.

regards

Simon Cork
Sheffield Uk