Can't see how adding weight would hurt. It might even let you use a descent slug or better yet, a round ball.

A shot-cup's hemispherically cupped gas check cut off the column, then put over the wads, cup up to hold the ball centered, then crimped over, folded or roll.

A .662" ball weighs 1oz.(16 bore)

A .690" ball weights 495gr. about 1 1/8oz.(14 bore -.693")

A .715" ball weighs 545gr. or 1 1/4oz.(13 bore - .705")

A .730" ball,weighs 583gr. or 1 1/3oz. (12 bore)