One thing I did learn was to not sit in the front row if you are even marginally obese!

We were on our first 800 a month or so ago to Puerto Rico from Houston with a Florida stop. We were one of the first to board, happily got a front row (my favorite on the other planes). We took our times getting stuff out of our bags and getting situated. I went to plop down and sat on both armrests! The arm rests are solid with fold out tray tables....

I was able to wiggle myself down, but it was very uncomfortable. We got up and made the march towards the back at that point, and got one of the last pairs of seats.

Anyways, I am obese but not COS and can sit in a typical seats comfortably with both armrests down and room to spare on the seatbelt. I think you need to be near petite to sit in the front rows comfortably!

We moved to the right LUV seats at the stop and it was ok for us.