AHU with VFD drive

May i ask, im designing an air handling unit but the space of machine room is not that big. there are two supply duct at opposite direction, so i decided to have a plenum at the discharge of AHU to meet the two supply duct. does this have great effect in the VFD drive of the motor?? I know that we are energizing the duct system so i think it is not a problem or greatly affecting the VFD as being not efficient. after all the pressure sensor is mounted in the duct not on the plenum. am i right??