One feeder per meal would be my recommendation too.
For the hissing, when she starts up with that don't put her away: keep her out until she calms down and stops hissing/striking/etc. My Hog can be a bit of a turd, and when I take her out sometimes she's hissing up a storm open with her mouth open and bluffing. I don't put her away until she's calmed and she's been acting much better from it: she's gradually getting out of her drama queen attitude. Just keep working with her and she'll calm down, it may take a few days, weeks, or months.