If you are going the SD route, I'd skip any kind of tub. Unless you are a breeder or space is really an issue.
Retics are extremely arboreal and enjoy climbing and perching. Obviously if you are dabbling in mainland animals, the arboreal part is probably not something most people can afford to do.
I find my SD X Dwarf X Mainland (only 18%) extremely active. I have two friends here who also had SD's, one pure and one a mix like mine. Both of those snakes were difficult keeps and both were placed. Their keepers felt cage size was important, and actually provided good sized enclosures. The pure SD was in a giant cage.
The pure SD was unfortunately a nightmare unfortunately and not all that small for a pure Kalatoa.
If you are just focusing on your own SD, why not give it some living space? They are excellent display animals and I think you'd enjoy seeing the smaller package display the wild behaviors they often show in captivity.
This cage is 6 feet wide, 2 feet tall and 30 inches deep. The snake is roughly 8-9 feet long.
With a pure SD, you could likely go 4 feet wide, 2 feet tall and 30 inches deep. I nice cage size for an active animal.
It doesn't get much better than seeing this action.
Honestly, this animal is about 50-50 arboreal and terrestrial. He is a real treat to watch.
Just my two bits, but I'd do yourself a favor, and really the snake too, and focus on caging as part of the experience.
UNLESS, you are a breeder keeping several snakes or don't have the space.
However if you don't have the space maybe the species isn't the right choice?
Best of luck, I hope you get what you want.