Pentatonic scales, passing thumb on black keys?

[Petter]

If you played a Gb major pentatonic scale spanning two octaves (all blacks Gb, Ab ,Bb ,Db ,Eb), I´m assuming you´d have to get the thumb under from one black key to another? Perhaps also in Db and B major pentatonic scales.  Any advice or insight? It doesn´t feel all that comfortable...

/thanks Petter