Hi. We are doing a bathroom remodel on the second floor and moving the toilet about 36" laterally. It is likely that the joists are running perpendicular to the direction of the move. Since cutting into the joists is out of the question, this would involve opening up walls upstairs and downstairs, per a plumber we've consulted. He said an alternative would be to install a back outlet toilet, eliminating the need to open up walls downstairs. Is this a viable solution? Thanks.