I have installed a new floor in my bathroom and now the toilet sits to high to make a seal with the cast iron flange it mates too in the floor. I have purchased a closet flange extension kit to remedy this. The kit has three plastic rings intended to be stacked to get to the right height. The sides of the plastic extension rings have notches to allow the bolts that hold down the toilet to pass through. Unfortunately these notches are so deep in the sides of the rings that they leave a small opening on both sides where I can see down into the soil pipe. The existing cast iron flange has an inner dimension of 5 inches. Do they make wider flange extension kits or is there another solution for this problem?