I really like the look of the spline tenons in a couple of Benson's recent books. I'd like to use some in a cottage I'm designing. Here's a specific question about them: The rafters are white oak, 7"x7"x13ft. Can I cut the through mortises (1" thick, 7" wide) for splines for the purlins (which are 4"x5") so that the purlins are 4' on center? there would be three such purlins between bents, and then a differently joined ridge purlin. Or would such spline mortises weaken the rafter too much? Thanks for your thoughts. Tim
