Follow want Jack advised before, I change the blocking plate of double-sided holder from a pull-out-push-in into a simply rotating design.
When the plate is rotated to show up, the camera is ready for double-sided holder.
And when the plate is rotated to hide in the chamber, it is ready for bayonet style holder, like Fuji PA-45, Grafmatic or 120 film holders.
This way, the camera is need no any parts to be taken off or installed back while changing the film system, no springs, no screws, no gg plates...., just a rotating plate to make all things done! and you wouldn't lost any thing in field.