I don't know anything about phase plugs, nor their proper installation and alignment, but I do know glue. I'm having a hard time believing that cyanoacrylate (super glue) would be appropriate for this job. Cyanoacrylate is not a very permanent adhesive. Its tend to degrade over time and doesn't stand up well to vibration. I would think a plasticized cellulose based glue would be much better.