Yes, the bottom is going to be a double layer. Also see pictures above. I have placed 2x6s across the bottom with 1 of them directly over the seam. The stand is also going to be very supportive of the entire bottom.He doesn't have an issue because he is correct! Compared to his three current tanks, this single one will absolutely save him time on maintenance, probably save money on power as well.
OP, I'm really looking forward to this thread. Good luck on the build. Is the bottom going to be a double layer, with the joints on each layer staggered with the other? That joint construction on a single layer looks sketchy.