It's actually better for a W/C to be the smallest tub possible that still allows for thermoregulation Jen while trying to get it settled in. Let me try to describe the setup that Adam recommended we use in Saoirse's early days.

We used a tub we normally use for juveniles (sorry I will have to run get the dimensions later). She had already been treated for parasites so we didn't go the paper towel route. We filled her tub very deeply with a natural type substrate (it was a mix of aspen and a lot of baked cypress mulch). So deep that basically her hides were almost buried and she had to go down into the hide (like they go down into burrows in the wild). We left a small amount of head room and of course a water dish. This does make the tub a tad harder to maintain temps and humidity wise. We put her in a bedroom and kept the curtain closed as much as possible (Adam suggested a walk in closet but at the time we didn't have one large enough). We allowed no one near her, no noise or disturbance in that room...heck we had her for months and our kids had never even seen her LOL. We offered her very small meals...nothing bigger than a large pup or small weanling rat. We fed her in complete darkness and monitored her feeds by sitting dead still close by and covering a low light flashlight with a dark t-shirt. As soon as she struck successfully we crept out of the room (she would not eat if any movement in the room was detected). We never handled her at all until she was eating consistently and had started to gain significant weight.

It's a LOT of hassle but for this one snake this worked. It doesn't always work and W/C adults can break your heart. Best of luck with this one.