I started out by fitting and drilling the right F-713 auxiliary longeron. On this one, I ground the 11 degree angle on the front before trimming the aft end. I'm not sure it matters, but it will leave me with a bit more edge distance for the most forward rivet.
I then spent some time figuring out the fit of the F-719 forward skin stiffener and the F-719B angle clip. The stiffener is about 1/4" too long as provided. The plans seem to show the forward end of the stiffener trimmed off square, but it appears that will leave only marginal edge distance on the forward skin rivet. I think I'll just notch the forward end of the horizontal leg to clear the vertical firewall stiffener. Once the stiffener is drilled, if the edge distance on the forward end to excessive, I can trim it then.
I fabricated left angle clip from a piece of angle left over from trimming the longerons. I'm going to wait until I fit it to the stiffener to drill it. (As I write this, I see on drawing 23 that the clip should be 0.063 angle. Oh well, I suppose I can use this one for a template...)
I needed a bit of help holding the F-719B for sawing.