There will be an unfair inequity in any "number" based definition. Differences of traffic, terrain, climate and commute distances have a major impact on ultimately attainable MPG.
Any Insighter interested in pursuing the "goal" will know from practice what their locally available ultimate MPG is. And we'll "know" privately whether that qualifies as a "hyper" MPG driver, or not.
Unfortunately this eliminates any "real" group recognition (unless you have participated in something like Tour del Sol, then that could make you a certified hyper miler
) since any individual could claim the title for any MPG number. But if we as Insighter's were interested in merely running with the pack we'd be driving something different. 
Hyper MPG'rs, we know who we are.
Any Insighter interested in pursuing the "goal" will know from practice what their locally available ultimate MPG is. And we'll "know" privately whether that qualifies as a "hyper" MPG driver, or not.
Unfortunately this eliminates any "real" group recognition (unless you have participated in something like Tour del Sol, then that could make you a certified hyper miler
Hyper MPG'rs, we know who we are.