Every toilet I've ever worked with (not many, I admit) has a stack in the wall directly behind it, including mine. I'm re-doing my bathroom and I'd like to install a wall-hung toilet. I have 2x4 construction, and Toto makes an in-wall tank designed to fit between 2x4s. Great. However, the diagram they give indicates my stack would by right in the way of the tank, and their document doesn't contain the terms "venting" or "stack" anywhere. Here is their installation guide (PDF)
What do I need to do to make this work?