[aerohead]

I believe that the Clarity is Cd 0.25. That's not a bad starting point for modding.
MOTORTREND's reporting on the 2016 Toyota Mirai, hydrogen fuel cell car had it an average 510-Wh/mi., and combined 67-mpg-e.
I don't know if the Clarity has similar performance, but if so, it suggests that 'Hydrogen' cars cannot perform at parity with BEVs.
Purchased new, some fuel-cell cars included a couple years of free fuel.
Kelly Pleskot of MOTORTREND's Mirai demonstrated real world mpg below the EPA rating. With a 56-mile daily commute, range was below 312-miles, and she had to refill the car twice a week ( see August 2017, issue, page 97 ).
Base price was $ 58,335.
2017 Tesla Model 3 started at $ 36,000, and up to $ 60,500.
262-Wh/mi.( actual ), 120-mpg-e EPA HWY, 2.225-gallons-e, 267-miles range 'HWY', as per EPA metric.. SUPERCHARGERS 'everywhere.'
The BOLT appears to hit it's EPA HWY rating at a constant 77-mph.