Duos are so overrated its not funny.
Unless you can find an ACUTAL Bi girl you wont have a good time.
Many girls talk a huge game on how great duo will be like the poster above, but in reality its nothing like your dreams/porn.
Bodies get in the way, you have to keep changing condoms, and the main reason girls love it is they get to do much less work (less than half as guys usually come faster in a duo) for the same money.
I would advice to just book 2 sessions with two different girls rather than duo.