Dave, i think then we both have reasonable doubt about the Cornu rotorcraft never getting airborn. I agree about belts having good possibility, and certainly Cornu paid them a lot of attention to avoid slipping - It was more an achilles heel.
The interesting part for me was Leishman's estimate of Ct/Sigma of 0.684. This seems to imply that the rotor was operating close, if not into, stall upon startup. At the very least the rotor was well into overpitching. Most likely Cornu had some successful moments, but the overpitching meant it was not repeatable enough to be caught on camera. A great shame. Pity too that he never continued development, with say lower disk loading.
Could you share some of your simulation results? I'm interested in seeing why you dissagree with Leishman's findings.