Well, I have taken some liberties in modelling the dual seater PAK-FA. Theis includes the auxiliary intakes, engine bay, exhaust and the overall shape of the a/c. So, while my render will not give a perfect idea of how a dual seater PAK-FA might look like, here is a side render anyway.: [link] Funny thing is that I used Mig-29M2's reference for modelling the canopy instead of Su-27UB/30.
BTW, thanks for your interest. I have visited your gallery and it seems that you have a nice imagination along with the modelling skills.