None of what you are about to read worked. I am joining the two Trim Tab club. On the first attempt I made folding blocks from particle board because I thought it would add a nice hard surface for a sharp crisp fold. It didn't. It flakes under pressure. Then I made the blocks different than the plan thinking I had better control over movement. My blocks put a small dent on the trailing edge fold and still the blocks moved such that I couldn't get the top fold in the right place. I did unfold it and try again and again about 3 times, until I finally cracked the skin. So I've ordered a new one. You can see in photo three the fold line is not centered on the radius but is too far inboard. I didn't like it because the I'd have to shave off some of the tab to match and the horns for the cable overhung the fold. And the location of the fold looks like a stress concentration point on the cut radius.