5200 is not a magic bullet either. I have used it for most of my life, and it can be a great seal, but I have seen it fail too. I am not real sure about how well it would adhere to glass, but the damn stuff is sticky as can be.
Regardless, my thought was to create an acrylic slot for the starfire that is 2" larger on all dimensions, fill the bottom with the appropriate sealant, and lower in the glass. I would hold the glass with pneumatic suction cups so that it hangs just below the contact point, and then fill the sides with sealant. Allow that to cure while hanging and when it was cured, I would release the suction cups, fill the top with sealant, and mount the acrylic top.
Redstratplayer: I would be very interested to see how a glazer would approach this project!
Thank you all for posting. I really appreciate the flow of ideas!