Another thing to point out. You really dont even need to put those diagonal supports on the sides either, especially if you cover the sides with 3/4" plywood, because that would hold it from rocking back and forth very well. I covered the sides with plywood and attached them with screws, that way i could remove them and make it easier remove my wet.dry if I ever had to.
Also if you look up my thread on my stand and take a look at the picture looking up from inside you will see the horizontal studs on the top are notched and screwed into the vertical studs on the back and front of the stand. that helps with the front and back rocking as well. I notched the bottom horizontal studs the same way. Another thing I did was every joint that you see it glued, just didnt want to take any chances.