Depends on your seating distance. I wouldn't go below 100" diagonal for an 11' viewing distance or 110" for 12'.
Seating at 1.5 x screen width for a 16:9 screen is an OK compromise which doesn't make lower quality sources too big or good scope DVDs too small
Seating at 1.5 x screen width for a 16:9 screen is an OK compromise which doesn't make lower quality sources too big or good scope DVDs too small