Re.Gann, What a writer, he was almost as good a writer as he was a pilot, and Fate is the Hunter was far from fiction.He most certainly had a considerable experience of the performance of large piston engine aircraft, as I recall he finished up on DC-7C, and was, at the time, one of the victims of the introduction of the "Age 60" rule by Pete Quesada, first FAA head honcho.
Back to "on the step", early editions of A.C.Kermode, "Mechanics of Flight" had a good treatment of the subject, for piston aircraft, some of the original graphs have slipped out of the later revised editions, as the emphasis has rightly changed to jets.
If you can find them around, the old "Pan American Navigation Service" textbooks on the subject provided some excellent coverage, with actual examples for the DC-4 and DC-7C. Sadly only of historical interest now.
Of course, it is quite (theoretically) correct to describe the "peak" performance of an aircraft, but in the real world of older airlines etc, the peak of L/D curve was so sharp that there was no speed stability, hence the invention of "long range cruise", a speed equivalent to a loss of 1% of max. range, in the interests of not driving the Flight Engineer crazy, ( and keeping the passengers on the edge of their seats with constant power changes).
As for the info. on boundary layer adhesion, the paper came from RAE Farnborough research, early to mid. 70's, I wouldn't even know where to start looking amongst 40 years of accumulated "items of interest" filed for Ron, Later Ron.