After contacting a contractor, I was informed that the only way to increase the size of an existing shower that is connected to another bathroom tub would be to run the plunbing on the outside of the home. The reasoning that there would not be enough space to work between the walls. The existing shoer is only 33″ with a total space between the walls of 56″. How large of a shower can be added within the existing space and still have room to work?