Dear Rabbi Kornfeld,
Our kollel appreciated your chidush on Sukkah 22b about how to measure the shade in a sukkah. We worked with your idea in shiur for two days. The rosh kollel felt that it explained Rashi and the Rosh beautifully.
The rav may wish to see the insights of Rav Karp. I think he suggests that only when schach and space are equal does the notion of tzel greater than sun come into play. Also, Rav Feinstein zt'l has a teshuva about a sukkah that has more schach than space on top but nevertheless has more sun than shade at the bottom.
Thank you again,
Shlomo Zalman Jessel