Hi Dan, and Welcome.

First of all, nice sketchup drawing. I assume that's why you posted here in the software forum. But actually, your post belongs in the design forum. This forum is supposed to be about issues with the software itself. One other friendly tip: When creating jpgs for popsting on the forum, drop down the resolution when you export from Sketchup, so the picture is a little smaller.

To answer your question, though, Brad's already given you the best advice: before you try to make up your own joinery, go back and look at historical examples. They're "classics" for a reason: they work, and have stood the test of time. In this particular case, you want to do some research on the English Tying Joint.

Again, nice drawing, and welcome to the forums. CB.