I doubt it but it's worth a try. The slop can come from just about anywhere in the system. The oval is shimed to keep the dome from being to tight and is pushed against the box of bearings that turns the shaft with the spring. Taking a shim out does nothing to make up for the wear on the bearings, the arm on the shaft, or the dome sitting in the horizontal arm of the shaft. Then you have the bearings on each end of the worm gear that wear. If you have excessive linear play in the worm gear removing a shim on either end of the worm gear might keep that from moving forward or backwards and get rid of the slop. Then you have the bushing at the bottom that wears and allows the bottom end of the shaft be sloppy. Generally taking a shim off the oval on top just makes it bind and be harder to turn but really doesn't take out any play. I wish it was that simple. Is there any oil in the box?