I have used a few Iris tubs and have liked all of them. Right now I'm only using the CB-80 and it's a nice large tub but maybe a bit tall at 12" for your needs.
Also, in the past I have been very impressed with the selection and service I have received from ReptileTubs.com. Unfortunately for them the Iris tubs I ordered have held up so well I have not had to make an order in years. I assume they are still as good of a company as they used to be.
Now, regarding how clear a tub is, I do want to point out that in theory just about any tub with flat ends can have an acrylic window installed to add or improve viewing. So don't necessarily limit yourself to just Iris tubs. If you find a solid colored tub you like you can always add viewing.
A lot of people keep cornsnakes in typical sweater boxes at 23" x 16" but I can't support this. And having kept racers in racks I would certainly want to provide something bigger than this.
Looking at the Reptile Tubs website, there are a few tubs in the CB/CF catergory that are larger than the typical sweater box.
One that stands out to me is the CF-750 at 28.75" x 17.75" x 9.5" -- I assume those are the measurments with lids so assume the box is more like 8.5" tall.
It is not as big as the other large boxes (CB-70, CB-75, CB-110) but it is taller and that really helps if you're trying to set up a rack with viewing area. I have found that when trying to build a display rack 9" is a good compromise between viewing area and space savings.
What I also like about this box is that the dimensions will allow a better yield for shelves when building a rack from the typicl 4' x 8' sheet material.
The CF-750 would yield eight shelves from a full sheet while all of the others would yield only four or five.
I believe this box has the exactly floor area as the CB-80 I use, which is about 27" x 14".
That's another thing to consider about boxes -- the thick rim around the top and the sloping sides means that the actual floor area is nowhere near what is listed.
If you're willing to spend a bit more money and give up a bit of size then the clear Polycarbonate tubs from Cambro make excellent display racks. On paper thise boxes look large but unfortunately they have a very thick rim which makes the floor space not much bigger than any old "ordinary" box.
But the display racks I have seen built around these boxes are very nice. I had some pictures saved on my old computer but don't have access to them right now.
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Currently keeping:
5.8 Gonyosoma oxycephala (Javan, mixed colors)
1.1 Philodryas baroni
1.0 Rhodesian Ridgeback