It only worked for me like that when I first got my projector, then I tried playing with it from a 40-45˚ angle and it was never straight again. Since then, if I put my projector on my coffee table, let’s say and angle it slightly up, but centred to where I’m wanting it, I still had to use the 4 corners, because it ended up with the top corners being way out beyond the lower ones. That was with the keystone on at 0:0 on all corners. A system reset is the only way to get the correct alignment again.
I tried turning the keystone off, and it resulted in a much bigger screen (8ft / 96"), but as in 1.0.24 the quality of the picture was like wearing someone else’s glasses that was the wrong prescription; it hurt my eyes. So, I turned it back on, and the quality did not go back to what I had before.
I ended up doing a system reset. From the exact same location, the projected image is smaller by about 8" each way, and although the quality is better (the pixels aren’t so obvious) i now have a headache.
I had a good picture before (maybe not shape). Messing with the keystone ruined this for me.