After getting the forming blocks like I wanted, I marked the flanges on the ribs using a piece of 3/4" plywood as a spacer. 3/4" is about 19mm, so it's pretty darn close. Using my rib forming skills, I carefully tweaked the flanges all around until I had a nearly perfect rib. I hope they all go this smoothly. Just for comparison, I think ZAC charges about $30 for one of these. Of course I still need to do the lightening holes, but I don't expect that to be a problem. One trick I used in making these was to use a 45-degree router bit to take out most of the wood for the crimp relief. Then I used a regular 3/4" drum sanding attachment in the drill press to round it out. This saved me a lot of time sanding and wearing down the drum by removing most of the wood before I got to the sanding phase. I also need to make up a couple of different size flanging dies to do the lightening holes. I've got a 95mm, but need a 115mm and a 65mm.