This piece of aluminum will go between the innermost fins on the cylinder barrel. I've notched the flange so that it'll bend around the corner when I rivet the flange to the flat piece.

Here is the more-or-less finished piece with the flange riveted in place.

An initial test-fit of the fiberglass baffles along with the aluminum backing plate and a foam block that I'm planning to glass around to form an intake to mate to the cowling.

I marked the an approximate shape on the valve cover baffling with black electrical tape.

I then riveted a flange on the aluminum plate to give me something I'll eventually attach the plenum to.

I had no clue how I was ever going to form the initial shape for the plenum so I just used about 1/2 a roll of cheap masking tape.