Update...work is moving along on the Ubi Dubium page, and a good number of panels have already been filled with knotwork, key patterns and zoomorphic interlace. A few areas have been partially begun and left blank until a wash of color can be laid down, after which the design will be completed. This allows for colored backgrounds behind the fine lines which otherwise would be impossible to paint between. There is historical evidence for this technique in several Celtic manuscripts, notably folio 30V in the Book of Kells where a yellow base fills several areas of the incomplete border. We can only detect the artist's working method because this page was never finished...possibly due the murderous Viking raids on the monastery at Iona.
Barring the improbable zombie apocalypse, I'm fairly sure that you'll be seeing the Ubi Dubium completed sometime this autumn. ;) The line work is nearly done, soon I'll be getting out the colors. More to come... :)