I don't like splitting them all the way open. Where I hunt in mostly thick stuff, that results in the chest cavity being filled with junk.
Anymore I often don't even remove the lungs or heart if I'm dragging them out and skinning right away. I cut the diaphragm and pull the guts out all the way to the butt hole. And leave the heart and lungs in there.
Works for me as I like to save the heart . Just one less thing to worry about in the woods.
-Jake