Borski - sorry - didn't see this until now.
Here is a link to the PNC Park Fan Guide. I don't see anything relating to flags, but there is a section relating to banners. If you can't find what you are looking for in the Guide, I suggest calling the Bucs' office - their telephone number is at the top of the Fan Guide.
They really need to update this Guide. It still mentions designated smoking areas - the smoking Nazis now prohibit smoking anywhere in the park. I'm a very considerate smoker and the smoking areas were away from the concessions stands and fairly private, but the first drunk who spills his/her beer on me or stumbles into me (which has happened umpteem times both there and at Heinz Field) - I'm lighting up!
I'll get a quick escort out of the ballpark, but I'll make my point all the way out the door.