How close you can sit depends on your projector. A CRT projector doesn't suffer from the dreaded SDE (Screen Door Effect), so you can either sit closer or have a bigger screen. With most DLP, LCD or derivative, the SDE comes into effect the closer you sit. I would go with the general rule of 1.5 times the width of you screen. Example: 110" diagonal equals 91.2" approx wide. (COS 34 degrees times 110") times 1.5 equals 136.8" or 11.4 feet. With the new 1080p projectors comming right around the corner, being able to sit closer with the same size screen shouldn't ba a problem.