Thanks so much for the responses. I for some reason wasn't notified of your posts or I would have replied sooner.

5TonsOfFlax, I dig where your going with this and I'll have to explore it in more detail. For the project, I actually had to settle for a workaround, but this problem has been gnawing at the back of my mind ever since.

I'm fine with disregarding scaling info. I even tried a system of equations assuming the blue corner was at z=0 in an attempt to simply things. Unfortunately I've made no progress. I'm convinced that a homography transformation is the key (http://en.wikipedia.org/wiki/Homography), but the matrix math is pretty deep, and even if I successfully calculate the homography, extracting the plane rotation from that is still a mystery.