Dunno about the -4, but on our -8A the backseat rudder pedals are virtually unusable.
My wife can't reach them at all, and even I can just barely move them a teensy bit with my toes.
I'm glad we've got the throttle and stick in the back hole (we're both pilots, and neither of us wanted to be helpless back there) but the rudder pedal mod seems to have been a waste of money, in retrospect.