Time to fit the center rib. The plans have you make up the attachment flange at the forward end of the rib out of a small piece of aluminum angle.

The flange at the aft end of the rib was integral to the rib, but when drilling it, the drill drifted, so I ended up having to cut that flange off and fabricate a new one from a piece of .032 thick material.

Again, fitting this rib took pretty much the entire day. I believe it is well positioned to prevent skin mismatch. Tomorrow, I hope to start fabricating the sub panel bulkhead flanges. Of course the ones on either side of this rib will be (mostly) straight, and outboard of the four ribs will have curvature to match the canopy skin.