I quickly cut a piece of plywood to set the sump on for the stand.
I cut it a little small, so I wouldn't have to cut it more than once

This will be hidden when the stand is finished.. So I really wasn't to worried about making it perfect.
I also replaced all the load bearing screws with real deck screws instead of drywall screws. The new screws can actually hold some weight, and are rust resilient.
I took my time and drew the lines to match my earlier drawing.. I actually used a square to make these lines. So now I can use them as a guide for installing my acrylic panels. The vertical line in the center is not drawn by me. It was where a divider use to exist in the sump. Though I will be placing a divider in the bio ball chamber. I will explain the reasoning behind that later.
Now that my lines are drawn I took a measurement of the depth of my tank (front to back). I cut a board to these measurements to see how it would fit. It fit.. though it appears the front and back of the tank has bowed at least 1/4". So I will use silicone to feel the gaps when I place the acrylic in here.
I cut up some of the pvc blocks I mentioned earlier in the thread to use as guides for the acrylic. My acrylic is not that thick, so these will help it stay square. They will also be used to hold up shelves in the sump.
I have placed one in this picture. I don't have much force on the clamp.. Just enough to make sure the pvc sits flat while the silicone dries.
Here I have two of the pvc pieces in.
And this is where my project sits for the night

Thanks to the wife for letting me use her parking space tonight.