Kevin, I don't have first-hand experiences, but I'm not aware of any particular rules or standards around signage so I think you have latitude to choose a solution that works for your building, provided you can justify it and it actually works.Your approach seems fairly reasonable, although I worry that it could be a bit too subtle. Have you considered markings on the sidewalk? Also, will there be butt collectors of some kind? These could be used to help indicate the designated area.