Yeah, I think it should make it a lower tune. I think it's something like a lb of poly fill per fubic foot makes the box seem 10% larger. Larger the box with the same size ports, lower tune. I could be wrong though.
Ive seen on many occasions where it is recommended to put polifill in ported boxes the only thing is that you need to staple chicken wire of some sort just before the port begins to shoot straight out to hold the polifill in place and it should sound a little better "SO I HEAR!"