[Midway]

I have many tangs in my 6 feet tank and they're doing just fine. They have ample room to swim and fight sometimes too...lol
My rock work is done with many crevices and caves so they can have some privacy and places to hide.

I have a PB tang and I have noticed that guy needs a lot of space to swim, he swims from one end to the other end of the tank in no time. Powder blues are very active swimmers and need lots of space. Now Yellow tangs in what I've seen in my tank, are less active and they graze a lot on the rocks, so they're fine with a bit less space IMO.

I agree with the others here, Yellow tang should be fine in your tank dimensions.