Diatonic Stacks of Seveths
Following up on a previous post grappling with stacks of semitones, here's a quick set of related fingerings. The first two are stacks of sevenths, then we do stacks of ninths, and finally a "bonus" set made by putting a second on top of a ninth.
Of course, these can be practiced not only in all keys but across all seven modes, giving plenty of nice sounds. The ninths are a bit awkward to grab but if you know your intervals all these are very easy to "see".
A good next step would be to do this for harmonic and melodic minor. Oh wait...
Have fun with these!