I measured the depth of film in a 4x5 cassete: it appears to be 0.210 inch. In t he Graphic ground glass frame, the deph of the glass in the frame is 0.150". Thi s means that the ground glass of 0.060" should be installed with the ground side to the viewer (and smooth side to the lens). Is this correct? I also measured L inhof Technica III (not Grafloc) groundglass: the depth is ca. 0.215-220, which is 0.010- 0.005" more than the standard cassette. Is this withing tolerances? In the Linhof, the ground glass is installed ground side towards the lens. However , the metal part holding the ground glass has a lit to it , indicating that a 0. 070 ground glass of slightly smaller size can be installed with the ground side to the viewer. Any comments or suggestions? I have not seen these distances and tolerances discussed.