Ken seems to have fallen into the trap of thinking that THXs 36 degrees is their optimum seating distance, when in fact it's where they recommend the furthest seat (back row) should be. They actually recommend 2.4 x the screen height for max immersion/image quality with good 1080 material which is 40 degrees for full HD 16:9 which works out as around 52 degrees for 2.35 screens when viewed from the same seat in a CIH set up.
The link I used to use for THX specs no longer seems to work, but this link to the THX Theatre Alignment Program has all the info you need in it. Section III part 5 contains the relevant info:
GaryEdited by Gary Lightfoot - 9/23/12 at 3:39am