We have tried speaker to the far right and Far left of the stage and found people in the front rows were distracted by the "image" of noise from the side but looking at the person straight ahead.
Hanging the speakers from the roof is difficult because they interfere with the projector screens on each side of the room.
Currently the speaker are high and central to the room. This position is contributing to feedback problems when we hire out the hall and people hold the microphone against their chest (despite being told to hold it up and speak into it).
The main issue I guess we are dealing with is balancing the audio quality with the visual presentation. These two issues are conflicting with each other in terms of speaker placement.