It really depends on how the uro uses it's space. More space is always better though. If the uro has enough room to remain active inside its enclosure, it will do fine in it until it gets a little bigger. In a tank that small though, you definately need to let it out to roam around. My mali was kept in a 10 gallon tank by her cruel past owner (poor girl), and her weight was up over 400 grams when I took her from him. Now I think it's about 275-300 (she lost a lot of weight in just a month). She still has a little way to go though. I keep her in just a 48"x13"x13" tank, which is by no means a large tank for a uro...it's actually a little small. But, I let her out once a day to run around so that she doesn't remain overweight. I personally do not think you can justify not letting the uro out to roam around at least every couple of days unless you have a tank that gives them about 15 square feet of floor space (like a 5'x3' cage), and maybe a little larger for more than one uro. With that setup you need tons of hides though for the uros to feel secure. The point is, if you don't let the animal out, you need to give it another way to get enough exercise, and the tank should feel very open on the inside while still allowing the uro(s) to feel secure.
that's just my 2 cents