Out of consideration for order people, but 3 seats so you're not taking peoples space next to you. It's not their fault you're overweight so they shouldn't have to have you in their space.

I'm a size 20-22 and honestly a tight fit for sure. Definitely get a seat belt extended organised if you are like me with a pouch and big behind. Also sit with others going with you if you can, as aisle seats had the cart bashing my thigh and middle or window I had to slide my big butt past the other passengers. I hope that helps. Also there are charts you can google for seat dimensions on different model planes. Good luck, enjoy your holiday.