Looks like you're starting to get moving on this project.
The only advice I have is that I would drill some holes in the PVC legs and zip-tie them to the diffuser just to keep things from shifting during construction.
How are you cutting the diffuser? I used tin snips, but find that pieces of plastic sometimes fly all the way into adjacent rooms. (I actually wear safety glasses when I cut it.)
i've been cutting it with needle nosed pliers, which works really well but does fling bits around pretty far
are you referring to the pvc legs under the main false bottom? i haven't attached them yet because i need to remove the whole thing to work on it outside the tank and having the legs on would make it hard to work with. when i finish it, i'll just silicone the legs in to the bottom of the tank and then place the false bottom onto them with more silicone.
i'm wishing i had some doors to open like they have on exo-terras... foaming the background is going to be a nightmare...