if you're looking to achieve the most heating bang for your buck, just keep in mind that your body loses heat most rapidly through your head and through your feet. Keep those insulated. Also, in spite of the fact that heat rises, for some reason it's always warmer the closer you are to the field. I suspect this is a result of the "bowl" effect of the stadium...trapping heat in. Also you don't feel the wind as much the lower you are.
Also FWIW there was a study done a few years back which found that skin to skin contact was the best way to keep warm with others
