Rocky - my father-in-law did the initial design of the Cessna 336/337 Skymaster aircraft as a consultant to Cessna (He designed virtually all of Cessna single engine planes in the time between 1948 and 1975, plus others). There are some interesting stories in this!
When he died 2 years ago, we threw out literally bookcases of design and other studies he'd done for Cessna, Beach and Boeing. He still had the initial 336 concept drawing that Cessna gave him in 1958 (the plane first flew in 1961) framed on the wall. He specified a boundary layer air intake for the 336 to cool the rear engine, but Cessna took the cheap way out and just made a circular scoop that did not cool sufficiently. He then did the detailed design for the boundary layer duct that became standard on the 337.
