I still consider any of the original Windtunnel models to be the "North Canton design". The Tempo; the grey bagged non SP Windtunnel you mentioned; and the SP Windtunnel. Yes, the motors have changed, and they are screamers - but the cleaners are still the same overall design that originally came out of North Canton.
All of the newer "T-series" and the "Bagless Pet Rewind" vacuums... I don't consider any of those to be much more than a TTI design with the Hoover logo slapped on to it.
