Haven't read through all the comments so may be late to the party on this one, but I seem to recall that GM had a mid-engined racing car using a similar concept (lightweight carbon-fibre flywheel) somewhere in the timeframe of the EV-1. Clever idea; one of its safety points was that if the flywheel were to become…

If you could take it up Big Tujunga Canyon between Sunland and Palmdale, I'd be interested in hearing how it handles that stretch of road.