These stiffners are a bit tricky. You must cut them to length and that is where the stuggle come in. I cut them a little to short so one of them doesn't make it to the top hole, Not a problem cuz it's just a brace for the skin and the important part is r
Cut them to length as in the plans
Cut the correct angle so it sits on the Long.
See a little gap at the top. It should have gone all the way up.