The rear spar doubler (HS-606PP) took me FOREVER to shape. You have to round the edges so that if fits snuggly in the radius of the bend in the rear spar. It is the first thing you do in the kit and since I've never shaped aluminum before, it took a while to get the hang of how to take off just enough material. Finally figured it out though. It was exciting to cleco real airplane parts together. The rear spar is pretty long. Ths HS is a lot bigger than I expected.