Anthony:

Here's how I fixed your spline:

Note that a spline is a top-level component, like any other timber, and it has sub-components to cut joints. Any part of the spline that's normally visible is not a joint - it's just part of the body of this timber. There are 3 joints: One cuts the slot in the beam, one cuts the front side of the through mortise in the post, and one cuts the back side of the through mortise.

See also this thread on thru-mortises

CB.

PS: Not sure why the picture is so small. Some kind of issue on the forum. Right click and dowload to your desktop if you want to be able to read the notes.