Well my main reason for asking is that I currently have a 46" TV in that spot right now and I feel like it's a bit big. My eyes always had to scan the screen, which I didn't care for. I've had it in the same spot for months, so I was definitely used to it size wise and doubt my feelings on it's size would change at this point. It was stolen last week though, so I'm replacing it now and figured that since it seemed a bit big, I would look into the 40-42" models, and also maybe get a nice set for the same $$.
I actually tried the cardboard cutout trick last night and felt like the the 40/42" would work fine, especially the 42". It's just hard to decide without an actual image to see. I guess I'll just have to buy one and see for myself, then return it if it doesn't work out.