Disclaimer: I'm a long way from even running the engine.

I tried to copy (at least in spirit) Tracy's install, as well. Renesis in RV-7. For fit (& financial) reasons, I used a Civic racing rad that has a more or less square face & is a downflow design instead of a crossflow 2 pass like the Scirocco style that Tracy used. It's around 400 cu in volume. One thing I intend to try is to use an exit duct. Because of this, my duct is on the engine side of the rad (Tracy dumps his exit air toward the engine). The layout in my cowl (I wanted as straight a shot as possible into the wedge) & the desire for an exit duct forced that change for my installation.

I tried to use the formulas & guidance from the K&W book as a starting point, but discovered that some of the stuff about wedges doesn't seem to match 'real world' application. Tracy saw my 1st draft & warned that it wasn't thin enough at the back of the wedge, & he was right. I used canned foam to re-shape the wedge to thin it out at the back. Once I determine that the internal shape actually works, I'll glass over the canned foam. I also used a turning vane in the duct to get more even air distribution through the core (thanks to Al Gietzen for that tip). The vane was needed because the inlet height is well above the center-line of the rad. I did try to use the K&W streamline diffuser concept to transition from the round inlet to the somewhat larger area of the entrance to the 'wedge'.

I used clear packing tape as a release on the flatter areas, and cheap electrical tape on the highly curved areas. Tape works fine as a release, but any texture on the form will get reproduced in your part. I had to do a lot of work to smooth the interior of the duct because of the ridges formed by wrapping the tape around the form. It's a lot like painting; if you do a lot of prep work, there will be a lot less finish (repair) work on the duct.

Shots showing the core I made, & the resulting duct with turning vane are on Photobucket at  

http://s1155.beta.photobucket.com/user/rv7charlie/library/radiator%20duct

Video of the airflow is at

http://www.youtube.com/watch?v=D0mUJdzzrG0

Charlie