Hm, are you suggesting that you want to take the LED fixture and rest it atop of a sheet of eggcrate that sits directly atop of the glad sides of your tank?
If so, without knowing more details of your set up, I am going to caution against that.
If these apply:
1. Eggcrate moves around a lot. I used egg crate on my rimless for a few weeks instead of the mesh tops while I looked around for clear screening.
Since there was no way to secure it onto the glass, when I would feed (Frozen foods or even flakes do not disperse well through the small holes) or move it to pick up a fallen coral, I had to realign. That's a lot of movement of your fixture for any little adjustment you want to make for your tank. Also, considering the thickness of the walls of the glass, I would not trust there to be no movement what so ever of the thinner egg crate walls.
2) I don't know how deep your tank is, or your tanks experience with the intense focal beam of such a fixture, but it would be harder to acclimate your system to the LED when the fixture is likely only 1-2 inches from the water line.
Usually, LEDs start 12-18 inches above the tank along with starting on a low intensity setting. Eventually the fixture can be moved lower, or just ramp up intensity.
There is the potential of course to start on a really low intensity during acclimation, but you also have to hope that the par value from the low intensity is enough to feed the corals! I don't know, but again, with only 1-2 inches likely above the tank, your initial intensity could be lower than is necessary to feed coral.
Solutions:
I also cannot suspend my fixtures from the ceiling. Instead, one of my friends built a bar system for me. It's essentially, a metal pipe (2 for my tank) bent at a 90 degree angle at the top and extended about 18" out. This bar was then drilled into the wood of my sump (with a metal connector).
A single hole was placed in the extended portion of each pipe. Then the hanging wires were threaded through the hole and tied off, and then the other wires attached to my fixture.
Done.
I could now easily change the height of my LED and had an easier time acclimating the corals to the intensity.
In the first few weeks I kept the light around 30% max for white and 40 for blue, then ramped up over time to max out at 70ish blue and 50 ish white.
I hope that helps given the fact that I do not know your system.
