I added the upper sides. They are pretty tricky since you have to do a long cross-cut. The book recommends using a jig saw. Unless you are a lot better than me, I can’t imagine that. I cut through it with the miter saw and finished it up with the table saw. Here’s the result.
Now, what to do with the error earlier? I used the miter saw laser and figure the angle is now something like 7 degrees instead of 5 deg. From the previous pic there’s still enough room to get a screw in the short side, so I dodged a bullet there. Trying to fix it, I set up my roller to the near side of the miter stand (never done that before) and cut a 7 deg cul through the part sticking up from the side. That went OK and if i push down the front of a arm test piece it looks like it will do the job.
Back side is undercut so it’s not an issue.
Noticed the arm support board now has a small crown. Figure I can fix that with my power plane. Hopefully I am over the worst implications of the earlier error.
-- Doug - When all you own is a hammer, everything looks like a nail.