I am building a 20 X 40 foot timber frame building. The bents will consist of three 8 x 8 whie pine posts supporting an 8 x 10 white pine beam. The tenons at the ends of beams are 2 x 9 x 5 inches long (I reduced the ends of the 8 x 10 beams to 9 inches). The 8 x 8 posts have a one inch deep housing on which the beam will rest. I originally cut these members last summer and since then, after becoming more educated on the subject of timber framing (through Timber Frame Construction by Sobon & Schroeder and various articles in the Guild publications), I am now wondering if these tenons are too short. Is a five inch long beam tenon entering an 8 x 8 inch post a candidate for failure? Is it worth the time and effort to lengthen these tenons to seven inches (and make through mortises)? This will also change the geometry of the braces and shorten the width of the building by four inches. I would certainly appreciate any input from people more knowledgeable on this subject than myself. Thanks for your time.