hi the mag drive units have very high quality parts and engineering. they have great quality parts available for experimentors as well.
i have trialed a couple and they can run a bit warmrunning12 volts. a pwm device is available o drop the power and by not have too strong an electrolyte the heat can be controlled. I tried one of the pwm Units and they woked great. i would be inclined to get four and wire in series to cut the voltage and they would be suitable for most vehicles.
For big volume gas production i think you need more plate area but 4 in series would give a good performance for most vehicles.
As i said make sure you keep the tempratue down and they should be great.
mark