Not with black ink. If you want to print ovals using "invisible" (to the AV) ink, then you can. The visible light readers use a red light and if the ink matches that color, then it is not seen by the reader. Otherwise darker ovals will produce false reads. Talk to Ian for safe inks.
>Is there a way to make the oval lines darker?
From GEMS readme.rtf:
1.4.1 Jan-7-99
Guy