Watch the Dm7/Bb7: Overview online guitar lesson by Jon Finn from Improv Target Practice
Here, the chords, scales and Target Notes are shown, described and Demonstrated for "Dm7 to Bb7". A few options for scales are offered. Notice that going from D minor pentatonic (over the Dm7 chord) to D minor pentatonic b5 (over the Bb7 chord) that only one note changes! The same holds true when moving from A minor pentatonic (over the Dm7 chord) to A minor Pentatonic b1 (over the Bb7 chord). Once you wrap your head around that, start comparing how many notes actually change going from one chord to the next. My point: "shapes" can very useful, but thinking about the actual notes certainly gives you much more information.