The floating bottom design is actually prone to failure for several reasons.
The most obvious is the weight of all the water in the tank is being held by the silicone on the bottom pane of glass.
A not so obvious reason for failure is the fact that, in addition to the water weight, decor and substrate, any upward force would have an equal stress factor....like when people put styrofoam under their tanks.
Placing the sides of the tank on top of the bottom piece actually gives you more surface area to apply silicone.
Placing the end glass inside the front and rear panels is a matter of opinion and I am of the opinion that strength isn't the reason, moreover, it is the fact that glass is purchased in standard lengths and having to remove an inch from a 36", 48", 60", 72"....etc...is more work. It is also my opinion that the exposed edges of glass is better viewed from the side than the front. Everything that is done to commercial built tanks is done for two reasons mainly:
-Build cost
-Liability
Liability is a risk factor that determines how the manufacturer builds the tank and they go by industry standard and experienced past failures. The point is, if you are building a tank on your own, it would be wise to "copy" the building standards of current manufacturers. ..they have paid their dues most likely and so-to-speak.
