Glass is in!
I installed each pane by pressing it in horizontally and then tipping the tank so the glass was facing down. I stacked a big pile books on top for weight. I only kept the weight on the glass for about 24hrs and then turned the tank back upright - I hope that was enough time. I used a lot of silicone (about 2 full tubes of GE-I per pane) which resulted in a bunch that was squeezed out and had to be cleaned up later. The seal looks pretty good but there are some small bubbles in a few spots (they are completely surrounded by silicone though so I don't think it should be a problem. I don't know if they were there to start with or if they formed because I didn't keep the pressure on the glass for longer.
You can also see the holes I drilled on the back for plumbing. They are 1.5" holes for 3/4" bulkheads. I drilled them a little oversized and then gave them 4-5 coatings of epoxy. They are still a little bit bigger than the bulkheads need so I may try to backfill them with silicone when I install the bulkheads to make absolutely sure I get no leaks.
The bottom of the green tape on the back is approximately where the water level will be. The two holes on the right hand side of the pic are for drainage and the one on the left is for the submerged return. There are two more at the top left corner which will feed the dripwall returns but they aren't visible in the pic. The other hole that's slightly higher up on the right hand side will ultimately be connected to a fogger/humidifier.