Once you get used to the band lifestyle, you will be happy to be full on 3-5 bites. It's when you have no restriction and can eat endlessly, because you are constantly hungry that is difficult...that's when your willpower has to control your portions.
Most can eat 1/2 to 3/4 of a cup of food, protein, veggies, grains and fruit (in that order). I rarely get to grains and fruit at a meal. I eat fruit for a snack, if I need one.
You will do fine!!