It looks great! It's a little taller than I normally build (That's like 2 Joe pens) but it looks like a 5'-5'-7" person can reach every square inch of floor space without having to crawl inside. The big pen is shaping up nicely as well
You can't go wrong with 1/2" HWC all around! Though, you should keep the wire top pen under cover. Under a pole barn at the least or put a hard top on it.