Last night I removed the focusing screen of my T to clean it and noticed that the mirror appeared shifted. There is a metal lip at the top of the mirror and it was not sitting flush against this. I gently pushed the mirror with my finger and it moved. So Im guessing that the screws that hold it in place are loose. Im trying to determine if I should set the mirror so it's flush aganist the lip and simply snug up the screws. If I do will I affect the focusing of the camera? Does anyone have any experience with this? Thanks for your help.