Last night I was listening to the episode "A Monikor for Your Monitor" when near the end one guy asked about the pronunciation of the word. After checking different sources, Grant advised that /hɪˈdʒɛməni/ is the right one and that some dictionaries had recorded /ˈhɛdʒəmoʊni/ as well, and that the other, /hɪˈgɛməni/, suggested by the guy's friends might evoke laughter if used in a formal situation.
Both of my dictionaries, Longman Advanced Dictionary of American English and Longman Pronunciation Dictionary (By J. C. Wells), have recorded that last alternative as well as the other two.
Without any rational foundation, I would probably pronounce it closer to /hɛˈdʒɛməni/. I agree that initial stress would sound very funny to me. But maybe it is the initial stress pronunciation that colors my pronunciation of the first vowel. Who knows?