I am making a bed and am ready to do the M&T joints on the footboard and rails. The footbaords and rails are 1.5" thick and 10" wide. I was planning on making one tennon, but after reading some posts, it sounds like I shouldn't make the tennon more than 4" wide. Being that I have 10" of width to work with, should I make two 3" tennons, or stick with the single 4"? I have never made a divided M&T joist before. Is it as simple as two tennons spaced apart by an inch or so? Thanks for the help.