Hello and Happy New Year! I am looking at plumbing 4 bathrooms (2 back to back on two floors right on top of each other). Please see attached sketch and leave me any comments you might see regarding connections or anything that you might notice wrong in the diagram. Also do I need a vent stack or could I tie in a 2" vent from the first floor with a 2" vent from the second floor and connect at top of the soil stack. I tried to fit everything in the 1st floor joist as the basement ceiling is low and the area under the bathrooms has a walkout area leading to the door. Thank you very much. I appreciate your comments.