Just to add my experience. I find that in order to get better airline
rates I am forced to travel into town on Saturday. So I'm in town on
Sunday with little to do other than catch up on work that really
should have been done before I arrived. So maybe doing more on Sunday
would be a possibility.
The problem with Friday is that after having spent a week at IETF I
really want to either get back home or to my weekend destination at a
reasonable hour. That usually means getting on a plane by 11am if not
earlier. So regardless of how important the Friday meeting is, I
probably won't be attending it.