I've read a few people in the past saying that PA systems should really be in mono, as very few of your audience are in the true "stereo" position.
I tried this last night for the first time, and all I can say is WOW!
It felt like I had a speaker upgrade - the sound - oddly - is much more full and "solid" sounding.
I really like it and will definitely be continuing this way. I was really surprised at what a difference it made.
If you've not tried it before, well worth giving it a go to see if you feel it makes a difference for you.