Another thing to consider is that your COG is above the wing in a low wing airplane and the the garavitaional pull on that COG is always straight down (and during a loop the centrifugal force acts perpendicular to the flightpath).

What's this mean?

It means in a low wing airplane at high angles of attack the force acting through the COG moves further back along the wing. Adding dihedral means the wingtips move backwards at high angles of attack to help with this.

This is just another reason to consider along with the many other ones listed above. Dihedral isn't there for any one reason, but roll coupling is usually the one we use dihedral to fine tune.

cheers