It also makes a big difference when doing rolling harriers down on the deck.

There is a guy at the field that loves doing rolling harriers "really low" (think wingtips in the weeds low) with his 40%er. He makes me nervous...why... because he doesn't use rudder and every time the plane goes through knife edge the nose drops about 10 degrees and the plane looks like it is going to go in.

Like everyone else said, don't ingrain bad habits.

If you are using the elevator only rolling circle as a stepping stone to learning full rolling circles, then that's okay.