Great work, layered object is a major bonus!
Ive notice there is also an alpha black and white image in the pdf file.


"""""""""""""""Seems there is a little quirk! ;) (tested on Adobe Reader 8 )"""""""""""""""""""""

That's because of the "Miter join" line property.
It doesn't show in all pdf readers though.

"Round join" wouldn't produce this type of kink.

Marc