Given the extra work, you -really- don't need to do it CleanOnion. Your formulas have been well appreciated since RS1.
Players should be looking at the 'Tile Location' anyway instead of simply looking for 'P's. The P/D wording was really an aesthetic I wanted to give to all players just for reassurance, given that RS2's "border" location-like system seems a bit harder to implement (and read even).