I decided that I needed to cut some lightening holes in these ribs for wire and tubing pass-throughs, so I laid out a set of holes that wouldn't interfere with anything else.

The fly-cutter worked to cut the largest of the holes, but the others were done with the nibbler. First is to cut a hole in a piece of scrap wood that is 3/8" larger in diameter than the desired size. That 3/8 is because the barrel of the nibbler is 3/8" larger in diameter than the little shaft that nibbles the material away. Used a step drill to create a starter hole.

...then just run the nibbler around until the hole is made. It doesn't leave nice edges on the hole...those will need to be cleaned up with some sandpaper wrapped around something cylindrical (I used a large socket). But, this approach beats the pants off trying to file these in.

All ribs done.

Jo had started a piece of material to make four flanges for the lower, aft end of the ribs. There is a slight bend in the sub panel there, so I had to cut the aft flange of the ribs short to avoid interference. Thus, I need four little angles to rivet to the ribs to create a flange below the bend on each rib.

Marked out some cut lines.

...then cut and filed them. Looking good.

I made up a little jig to drill them very consistently. Here, they're drilled to #40, but will eventually drilled up to #30.

Well, crap. I can see here that I shouldn't have drilled the flange of these angles that mates up to the sub panel. The rivet holes won't be in line with the rest of the rivet holes.

...sooooo, I made four new angles. This time, I drilled the holes in the sub panel, then transfer drilled them through to the angle.