Okay, better clarify here. There were three backs for this camera family: the Graflex back, the oldest and common on pre-War cameras, the Graphic back (most identifiable by the non-removable focusing panel mounted on spring leaves), and the Graflok back. Pacemaker cameras mostly had Graflok backs (they were offered after the first or second year of production), and I don't know that they were ever sold with Graflex backs
A Graflex back has only a single movable locking slide and a rib where the Graphic and Graflex backs have a groove; the film holders for it would be grooved instead of having a rib like modern standard film holders do (they're also slightly wider). It's FAR more likely your Crown has a Graflok back (two movable locking slides and a groove to accept the rib on a modern type film holder) than a Graflex back.
What this means is that the bag mag, almost certainly made for a Graflex back, is too wide to fit a Graflok and lacks the rib-and-groove interlock of either to keep the magazine from pulling out when you remove the dark slide.
Back to the original question, bag mags wouldn't have been popular if film damage was a major concern -- what do you gain loading twelve shots if you have to shoot half of them on a single subject to be reasonably sure of getting one undamaged sheet? If you can mount the mag, you would do very well to practice manipulating the septums inside the bag (pulling the front one out of the frame gate and slipping it into the back position).