I have a cast iron toilet flange that is broken off where the toilet bolts go, as shown in the pic below. I was going to use a pair of those flange repair brackets, but I am concerned there is not enough flange left to make a good seal when the toilet is installed, so I think it would be best to replace the flange. Should I remove the flange from the pipe, and install a new ABS flange that inserts into the old iron pipe with a rubber seal? Or should I cut off the iron pipe just below the flange fitting? Backerboard is to go on top of the plywood, then tile. It would be nice to remove the toilet flange, finish the floor, then insert the repair flange, screw it down to the floor, then tighten its seal expansion bolts, and voila - done. But what if the inside of the iron pipe is rough, pitted, etc, and the replacement flange doesn't make a very good seal to it?