With those little angles drilled to the sub panel, I setup a jig to drill the holes for their rib attachment rivets.

Well, that's frustrating. Yesterday when I was making these, I decided to make them 1/32" longer than the first ones to give me just a little more edge distance on each side. But when I drilled these holes this morning, instead of splitting that 1/32" between the two sides, I put it all on one side. Grr.

...so, I filed these holes oblong so that when I drill them up to #30, they'll be in the right spot.

Better.

Of course, that made it a pain in the ass to match drill through the #30 holes into the rib. Match drilling #30 through thin material like this (.025) is likely to result in holes that drift out of position. So, I used a piece of brass tubing to center on the #30 hole allowing me to drill a #40 starter hole.

Now drilled up to #30.

Here are all four angles.

Dimpled everything so that I could use AN426 flush rivets (flush head between the ribs) so that I didn't introduce obstructions for installation of the popup tipup arms or UHMW side guide sheets or spacers.

Also, I dimpled all the holes in the firewall flanges.

Lastly, I deburred a big pile of parts in preparation for priming.