I purchased two of these kits.
https://www.lowes.com/pd/2x4basics-..._clickID=7d756ab7-c81e-4b34-8d2a-5114b1719700
Make the top size anything you want. Extremely stable when fully assembled. All you need is a powered screw drive and something to cut the wood you purchase with.
Want to sit at the bench? Make the center shelf out of what you cut off in length from a sheet of plywood. Then the center shelf ends up only taking up a portion and offset to the back and you can sit on a stool with your feet on the lower shelf.
If you buy through E-mail you can get them for the same price with pillars that go on top of the bench. Use the narrower sheet cut from the second sheet of plywood for the top and put a sheet of peg board behind.
I went full 8 feet in length, but 32" Deep with two 18" pieces left for each bench. One for the top of the pillars and one for the middle shelf.
Bob
Bob