Nellis, very nice tank.
I did same extensive research in this matter as well. Luckily I'm native German and was able to research at the origin of the ADA tanks on procedures for building rimless tanks.
You are correct in placing the side panels against the bottom panel. In my local group we came to the conclusion this would be because of the properties of the silicone.
If placed on the top (of the bottom glass), the hydrostatic force on the seal would be in a shearing motion (trying to rip the seam apart along the horizontal). However, when placed on the outside, it would be in a pushing motion and gain increased surface area, tension and friction to overcome from the bonded strength of the material. I believe silicone has the ability to stretch, but not counteract a horizontal loading.(Credit to gmccreedy)
But elevating the bottom panel you would create the same shearing motion as you would have with placing the side panels on the bottom panel. Also the energy created on the bottom seams is the biggest in the tank, bigger shearing motion. I think the best bet is to not elevate the bottom. One more issue you are creating with this design, all the weight has to be carried by the small sides of your side panels. One small pressure point would cause the glass to chirp very easily. If you look at ADA tanks, those don't have the bottom elevated and ADA recommends to use the garden mat (a must for flat bottom tanks, neoprene being the most suitable for this task). The garden mat will clear up the argument for a cracking bottom as well, you just can't place a rimless tank on a none protected surface.
To overcome torsional pressure mention by you for bigger tanks (I think over 90G) you are not supposed to use a single piece as bottom panel. You are supposed to use multiple pieces and even two layers of glass glued together to allow more motion.
Nate - I don't want to say that your tank will fail. Due to the small size your tank can be completely stable. But somebody else attempting to build a rimless tank should know the issues with a elevated bottom.
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