I'm getting ready to build and I've heard some newbies (like myself) getting gently chastized for coops that are 4 3/4 by 16.2342415. Math is not my forte (or even my pianissimo) so in simple terms (or just tell me) what are the efficient dimensions are. 8X8? 10X12? Square? And I suppose, what is the most efficient wall height? Thanks!