Try working "inside the box", so to speak. Yes, its regretable that one can't play a chord and have the harmonizer yield a full chord. Instead, try building a patch with two octaves (one +12, and one -12) and blend with the original. I've made many "POG" type sounds with the PODHd500 that were very close to Joe Satriani's "Super Colossal". Maybe add a little octoverb and you'll have a real thick sound.