A heavier sinker won't get you any further in distance unless you are casting into a headwind. What kind of sinker are you using? As long as it has good strong long wires, there should be little issues. The down side to extra weight on the sinker, means those tentative small snapper bites usually shy off along there.

I would move to 40 LB on a 6 ounce..... The gun casters tell ya 10lb an ounce, but your not casting over grass.......never snapped the 30LB leaders, and the rod gets a fair thump.