Thats surprising treated lumber is bowing that much!
That plywood design is similar to the stand my 125 came with. Always worried me though it was all furniture? Grade plywood (chip board stuff) but all the weight was actually supported on about a 1/4" lip all the way around the inside. It worked because vertical support went all the way around just did not care for the setup.
As to the above mentioned, if your not a regular wood worker or cabinetry person over build and sleep sound!
I am doing my next stand based off diyfishkeepers urajoey style listed on youtube very easy and is a very stout design!!
Sent from a dark corner in my happy place
Sump Pimp #8
RAOK Clubber #28