Glad you liked it! Sometimes it's important to stop and think about how basic physics really impacts our tanks. I think a lot of reefers knew that the black backgrounds wouldn't reflect as much light, but it was pretty shocking to see with the laser demonstration in this video.
Finding a material to replace the the back covering would be a large step forward in terms of uniformity.
The front/ sides have index of refraction for Water/Glass/ Air of 1.3/1.5/1.0
The back is Water/Glass/Acrylic (paint binder) 1.3/1.5/1.5
There are no standard materials with an index of refraction close to air, so the ideal solution may be a false back. Something like those plastic sheet window insulation kits would work. Apply some double sided foam black tape around the perimeter, roll out black plastic wrap, cut it then use a hair dryer to make it tight. Since it is slightly flexible, you could still use magnets and such to mount things to the back... Sounds like a good BRS product!