On smaller frames using 6X6 post/beams and 4X6 braces and rafters, simple mortise and tenon joints for the rafter tops work great for 12/12 roofs with no ridge beam. How much could one lower the pitch and still not use a ridge beam? Can anyone reccomend a book or literature that covers this? The question applies to 12X12 covered gazebo's made of doug fir. Thanks, Jay