Mine is about 29" wide I think.
But the shortest board I have paddled is a 9'0 Mana I think. Just checked, they are meant to be 29"5/8 wide, which I thought was enough.
However, I fully concede that extra width gives stability, floatation, etc.
I think unwritten Rule No.1 is still "the winner is person who is having the most fun!"
And when I think about, if I went Sub 9, I would probably need the width and extra foam !