I am planning for a 1.5" Bean overflow. My understanding is that that will provide more flow than my two 1" Dursos that I currently have. I am considering the external box, but since the tank is up against the wall (see old pic below), I would have to plan for the bulkheads to be between two studs so that I can cut into the wall to run the pipes down. Also, based on the reading I have done, it looks like I need a lot of linear drain, much more than 32"? I suppose I could go with a toothless design.