I've been using IME forever, but just learned how to do this. I thought I'd share:
Alt + Caps Lock is Hiragana -> Katakana (Full width)
Ctrl + Caps Lock is Katakana (Full width) -> Hiragana
It's better than manually clicking to switch, though it will probably take some time for my fingers to get used to hitting those keys quickly as I type-- it figures though, those are awkward key combinations.
Anyway, enjoy, and I hope not everyone knows this already.
Alt + Caps Lock is Hiragana -> Katakana (Full width)
Ctrl + Caps Lock is Katakana (Full width) -> Hiragana
It's better than manually clicking to switch, though it will probably take some time for my fingers to get used to hitting those keys quickly as I type-- it figures though, those are awkward key combinations.
Anyway, enjoy, and I hope not everyone knows this already.

