I checked EBC's site and the DOT brake pad codes. It looks like any pad with a coefficient of friction between 0.55 and 0.65 is considered HH. EBC does say the GPFAX pads are race-only, very high friction and not recommended for street use. They're only good for racing tires on a race-prepared surface. I learned something today.
I may try their EPFA pads on the H2 next time, which they say are based on their HH pads, with some additional ingredients.