Yes. Very sound. In fact, there is a good chance the center board in the last shot could be pulled out as it is not really going to support anything. Can't imagine what amount of pressure it would take to make an 18-20 inch piece of glass bow along the vertical side and the bottom is not resting on the boards anyway so supporting it is not being done, no matter how we build the stand.
The only critical point is getting the four corners level. Many people confuse their tank failing as being lack of support when the real cause is uneven support. One corner even 1/4 inch higher than the rest will certainly put lots of pressure and make a glass split.
This is a place where a laser level is super easy to make certain the four points are correct. But then a long bubble level can work but just a bit more care needed to read the bubble accurately.
Do not trust floors to be level and true as they rarely are totally correct, especially concrete.
Last edited by PlantedRich; 09-17-2017 at 02:48 PM.
Reason: added info