The cooling duct is a big complex piece of fibreglass. I was amazed that it appeared to fit well. The plans call for it to be clecoed on, so you have to drill holes through the cowling into it. At this point it is apparent that the cowling needs to be translucent to see the flange of the cooling duct inside. With my black cowling this was all the more difficult, but with a backlight inside the cowling I managed.
Picture 1 is looking into the "mouth" of the cowl. You can see the hole where the oil radiator fits. It's currently removed.
The rear right-hand cylinder head is a tight fit against the cooling duct. See Picture 1.
The third picture shows the number 2 exhaust header pipe touching the fibreglass. That won't do. In spite of everything else fitting so well, I had to drill more test holes in an attempt to lower the duct somewhat. I managed to create a little space, but it is still minimal, probably too small a gap for comfort. I may have to retrospectively cut a hole in the duct and make a bulge to accommodate the exhaust pipe.
