I have a one story ranch with two bathrooms that both need venting. They share a wall and I am wondering if I can get away with one exhaust vent for both fans. Does anyone know of any problems I might run into if I mate the exhaust for both fans in the attic and run them out one vent? Obviously a backflow prevention gate on each would be in order. Any other issues? I would like to avoid putting more holes in my roof than I have to.