Finally, I managed to get it right. Mapped the number keys closest to the "joypad" for the shoulder buttons. Dash and backspace are B and A respectively.
Runs extremely well and as soon as I can get used to only using my thumbs instead mixing in my index fingers, I'll be spitting out beats like a madman
A tiny gotcha is the application seeming to override the ctrl+q hotkey to quit an application when running with Fullscreen = YES!