Thanks everyone! As for using a kreg jig, I have no idea. I'm not any sort of master work worker, so that's something you'd have to look into.
Hoppy, you are spot on with regards to the weight capacity on the acrylic. I'm not sure it could even support a second finnex unit like a Monster Ray, but it might. I'd have to try it. As for any non-led unit, I don't think it'd have a chance. Also, I'm curious about your thoughts on the proportions. Are you thinking of where I chose to put the lower cross unit? I wasn't entirely happy with that after I did it, but it's done. I think it would look better higher up, but then I couldn't fit all my equipment under it. My Fluval 306 sneaks out with less than 1/4" of space.
Otherwise, the width matches the tank, the depth is as shallow as I could go with these supports (which is 2" past the tank in back), and the height is to make it perfect viewing height for my chair that sit's immediately beside it.
I do think the stand it's slightly imposing for the tank. However, with the way it sits normally, much of the stand hides behind my chair (the plant to the left is normally up against it, touching it):