I am a bit afraid I will tell you that!
This is somewhat of an experiment, but I also feel it is doable! The fact that it has been over 48 hours and "all is well"...
I promise I will keep an eye on any problems and secure any flopping

fish promptly.
One of the things that happened when I assembled this mini-monster is the tanks were not aligning with the each other vertically square. Basically when I pushed the two tanks together the bottoms would touch but there was about a 3/16" gap at the top. To remedy the problem I shimmed the "low end" tank from its end in the "up" direction about 3/16". This made the glass alignment "more" tight. After squaring up both tanks, I siliconed the shimmed tank to the plywood base so it would not move. Then I pushed the other tank square (after siliconing the joint). This essentially pressed the ends of vertical pieces of glass against each other. Its almost like one tank is slightly wedged into the other. To me, this seems to make the seam a bit more "tight". I guess time will tell? But seriously, when does a tank fail? One week , one month...I have tanks that are forty years old and have been thrown around like a rag doll and that still hold water.
Wish me luck!