If you sit anywhere between 2 to 4 times the screen height, you'll be in the range of most theatres seating. The geometric centre of the seating is often around 50 degrees, which works out around the same distance back as the (scope) screen is wide which is roughly where Hogpilot sits (so do I). Where do you like to sit (if you are able) in a commercial theatre? 2 x the screen height is considered the closest recommended by SMPTE if you're interested in industry guidelines. THX recommend that 3.68 x the SH is the furthest seat.
As Hogpilot said, experimenting is often the best way to find out what suits you before buying a screen, but many first timers don't realise how close they sit in a commercial theatre and often end up sitting quite far back at home since they don't think about seating distance as being important or consider how close they sit in a commercial theatre. Your seating sounds fine though - is that screen 128 ins wide or diagonal?
Originally Posted by elmalloc
Who says Cameron is "right" and why do we care about him so much - lol!
I trust Gary Lightfoot more than James Cameron.