I hope you figure it out because I'll piggyback on that knowledge. This is one topic that has eluded me and given it's easy to deal with flipped images and re-centering I haven't found it too big a deal not to figure it out. But once in a while, I'd like to do it but haven't gotten the right formula down yet. I always use SGP, and precise centering/solving, so maybe this further complicates things.
