I formed the stabiliser ribs as per the wing ribs, sandwiched between a form block and a blank. These all have a flange on the same side, the only opposing pair required is for the end ribs, which have a formed nose section.
As you can see from the images, I first cut the blanks, then drilled a hole at the intersection of each flange corner. Trimming this later then provides the relief hole when they are bent into shape.
