I was wondering about this... I built a 17" (folded) originally I used the 'standard' LL lens and built a screen 4'X8" and on widescreen movies this seemed okay but the PJ was only about 8' from the screen...
I rebuilt using a pro lens and using the room I wanted to use as my projection room I moved the PJ to 13 feet now my image is 7" tall! this is projecting my computer screen.. I'm sure a widescreen would be shorter but if I want to use it for games it looks like I will need a LOT bigger screen right? Does this image size sound right?

4/3 is tall. I have the same problem sometimes. My screen is is 117" 16/9 and for the old movies in 4/3 I have to make the image only about 60x70. I used some extra material to add on the bottom to make it about 90x100 which helped.

There is 4/3 16/9 and 2.35/1 no one screen will cover all.

If your screen will roll up you can adjust it fairly easy but if you want to cover all ratio's it's going to be wide and tall.

For my outdoor screen I want good 16/9 and great 2.35 but I still have some 4/3 stuff so it looks like the final screen may be 85"x160"

I tried my new 2.35 62"x142" indoor screen with Pirates 3 and it looked impressive.

You would be surprised how hard it is to see a seam, when just hanging a piece of fabric on the bottom of the screen, at a 8' seating.

On my first build I had his problem and probably will on the second build I working on.. I use the program that came with my nvidia card to adjust size a little bit .. But watching movies I use crop in VLCmedia player and make it fit my screen.. Also BS Player has a nice feature for that... as far as the tv function I use a win tv card and use the crop feature as well to get it just inside the screen.. For the computer itself it hangs outside the screen a bit but not to bad.. I dont really use it for a computer .. Thats what my laptop is for....