i got a 35 qt tub for my 4 month old bp (who's also almost 2 feet long) about a month back, and he seems pretty happy in it.. the tank does seem big for him, but i've kept about 3 hides, and water bowls, and have used aspen bedding as a substrate.
i've used a cardboard box on the hot side with a small water bowl inside it, a tree - bark hide on the cold side, and another cardboard box in between.
i've also torn up some toilet paper and put them in the hides, so he can snuggle / burrow into them. i've also put a tube of kitchen paper roll for him to hide in, which he does pretty often.
i'd originally drilled holes into the sides of the tub.. about 6 each on 3 sides of the tub.. but later, i found a window's mesh, attached to its frame, whcih fit perfectly onto the tub, to act as the lid..
this kind of brought the humdity down, so i put a damp towel over half of the screen , which keeps the humidity around 55 %.
he's kinda happy with this setup; he moves often between the cold - medium - warm hides and at night, when i shine a torch into his cage, i've often seen him moving around..