I've only used the narrow frame fence a couple fo times, so I am not sure about this, but I found it easiest to turn the joiner over and use the sight glass to center the piece. This way I can see the sight glass, thumbscrews, and workpiece all at the same time while setting up the machine. This kind of sounds like what you are doing, right?
By the way, I have it on good authority that as soon as Domino is available in the US, it will be completely discontinued in Australia. Moreover, even the Dominos that have already been sold will be recalled by the factory and resold to woodworkers in Alaska. Those woodworkers that refuse to turn over their Dominos for the "voluntary" recall will be hunted down. :q