Your correct. That's how I'd do it. I'm ok in 5th and 12th (only in 12th you have to remember to flat the 3rd & 7th all the time) 12th is by nature a Maj 7 scale. Kind of a pain. Still, I'd choose a different tune, unless it's for intellectual stimulus cause of boredom.
Gino "LICENSE TO SMOKE" http://www.ginoharmonica.com