Iam trying to put in a shower and the drain is about 2inchs off. I have cast iron piping and only have 8inchs available to connect the boot and pvc piping to it to move the drain to fit. The pvc piping I found meassures 12inchs and I only have 8 inchs available to make sure I don't cut into where the water sits in the p trap. Any idea on an easy way to get this drain moved over?