Both upward and downward stems inside a tuplet?

Hi,

I cannot figure out how to flip part of the notes in a long (20 notes) tuplet. First there are 9 notes for a right hand (stems pointing upwards), then 4 notes supposed to play with a left hand (stems pointing downwards) and finally again 7 notes supposed to play with the right hand.

Is it possible that inside one tuplet there are both upwards and downward stems?

Thanks in advance!

-Jani