Uro's are burrowers, so tank height is not so important. Hide size should be big enough for him to turn around in. If you're doing more than one hide, make one large enough for two beardies to be in and you'll be set for additions. Two single sized and one double would be ideal if you plan to get another uro.
Will you be using washed play sand for substrate? If so, you can also add pvc pipes for tunnels underneath.
Here's a link to some cool photos by a uro keeper who used styrofoam:
ImageShack® - eric35's Profile Page
I can't find the link, but I've also seen black folding/accordion pipe used and would be my personal choice for tunnels since you can easily make curves. Also they come in large sizes at the hardware store.