Unfortunately, you are using an out of date browser which is not fully compatible. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
It works best with fairly undefined edge patterns. As you know, whether
mirroring or not, trying to stretch something that has a sharp line or stripe
at the edge can be tricky, especially when a canvas stretches more one
way than the other.
I posted a video on my YouTube channel a while back that demonstrates how to prepare a digital image to be printed as a gallery wrap. It covers "mirrored" edges. Might be helpful. Here's the link: http://www.youtube.com/watch?v=dq9RhrS30j8&sns=em
Our guy also prints black lines on the remaining white canvas, out past the edge
of the images, signifying where the center of the mirroring falls. Makes it easier
to measure for the stretcher bars, just going from line to line.