The 'virtue' of the 21 bar 'harps is that you can move them around to suit your style and the common chord combinations.

When I got a 'new' one maybe 15 years ago, I reversed the default layout, then re-cut one bar to give me a D-maj.

Now I have a 3-finger pattern for most of the regular major chords, and the ones I use most are in the middle.