Will using Flawless Widescreen for single player get me PB banned?

This is a community based support forum where gamers help fellow gamers, so you can't expect EA/DICE to respond in here as it's not direct customer support.

Now, I believe nobody has answered you because nobody here knows the answer or can say something besides what you have already been told. The program apparently "hacks the memory" which can cause a Punkbuster ban/kick.

It might work, but I don't think you will find anyone promising you wont get banned as it's a third party program.

Personally, I wouldn't use it.