I know I am being pedantic here so please forgive me for the quintuple post, and kudos to any of you who have followed me this far.
One of the Prime reasons to make that short 2x4 short is so you don't have to measure and cut it exactly. While all the posts should be exactly the same length, unless you want to shim up a crooked stand, the "lap blocks" do not have to be any specific length as long as they are long enough and yet not too long.
The ends can be a little crooked or have a knot, and it doesn't matter because the ends aren't supposed to touch anything.
As soon as they do you can apply unexpected loads to screws and members which were not considered in your calculations.
Fortunately the DIY Joey type stand is cheap and so overbuilt for most of its needs, that it works pretty well even if you do a sloppy job.
Thank you for taking the time to respond to my thread throughly.
I’m am by no means a good diy, I would love to take the suggestion from above an design my own stand but alast I do not trust myself. So I wanted to use someone else’s design that has been tested and known to work.
I plan to installed side panels, a top, a bottom inside the stand and some kind of door or doors on the front with maybe a half shelf on one side for storage.
I do not plant to install a backing on it whatso ever, unless needed.
I also do not plan to use fancy pocket holes, just straight up screws into the wood, depressed into the wood with maybe a wood filler over the screw holes. I don’t necessarily need beautiful, just decent, and functional. The stand that came with the tank is not reliable for myself as it is on casters...not good for the weight on wood floors.