I've seen a few people use square manifold bodies now and got curious.

Found this article on manifold design:

http://horsepowercalculators.net/intake-manifold-design/intake-manifold-design

Interesting read. It helped clear up some misconceptions I had about the proper design of an intake manifold not having any fabrication experience. For instance, I would have thought having runners flush with the bottom would cause less resistance, but it turns out that is a big no no because velocity is extremely low toward the bottom of the body. It's the only source I've read though, so I won't say without a doubt that everything in it is definitely right.