This happened to me recently where two large men were seated next to each other and I was in the aisle. I offered to sit in the middle. We had a lovely flight, chit chatted, read our books, and everyone was comfortable. (Although they did tease me about my number of bathroom breaks.) I think airlines should stagger people. Small people in the middle. Larger people on the ends. Or even have different sized seating sections. This isn't hard. They have the money to do it.