Just an after thought. Right now we know, for sure, that one of two pixels are "bad" because of the lack of signal or the wrong signals going to the remainder of the string behind it. With the backed up versions, are we going to be able to find bad ones?
For example, if it is the output of a pixel that is bad the pixel itself is lighting. We may never know that this output is bad because the next pixel will be lit using the information in the backup line. Not that it matters that much since the string is working, but it is something to ponder.