I have an old Calumet 400 with a spring back, and recently loaded a Grafmatic fi lm holder with film only to discover that it doesn't seem to fit the Calumet. Th e Grafmatic is fairly thick and is stretching the springs of the camera back to what looks like their limits. While the film holder goes in 3/4 of the way there is a ridge on the Grafmatic that prevents it from going in any further. I'm war y of exerting any more force to try and squeeze it in. Am I doing something wron g, or is the Grafmatic just too thick for the Calumet back? (The Grafmatic fits fine into the graflock back of a Speed Graphic I tried it on, of course.) Any he lp would be appreciated.