So I left FI's side of the family up to his parents to track down the people that didn't RSVP. Well I guess they didn't call everyone because today 8 more people are coming that weren't before.
So I am pretty upset that people are so rude as to come to a wedding and can't bother to RSVP. So they will be split up at tables because of this. That part of the family is known for not RSVPing also I guess. AWESOME.
So I should have been more particular about this a few weeks ago- lesson learned. Vent over, beer in hand.