I have a pair of racks, but I plan on going down to just the big one in the middle. Going to be making slight modifications to the adult rack and the rat rack and selling those off.
28 qts are fine for males, especially those that are maintenance fed and tend to stay smaller than females. For females, you're going to want a 41 qt for adults, which is what the rack in the corner was built for. I used simple plywood for both my snake racks, though the bigger one is intended for multiple sizes and if the slot is too loose for one size it allows for the lid to be kept on the tub. If it's tighter, I remove the lid (which I prefer).
Super simple build for both, since it's basically the same thing for both but with different dimensions. Plywood with 1x2 studs on the bottom sides and back (sides so that the shelf can be attached to the legs, back for a backstop to the tubs). It's a pretty common plan that you can find here on this site or even on youtube. Honestly for my next build I may go melamine since the plywood can warp in high humidity, or even xpvc if I could find it.
Edit;
found my designs for the adult rack. Not super detailed and more of a shopping list with a doodle, but it's what I have.
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