Lee sells a range of 3" / 75mm technical filters. For example, CC40Y (Yellow - Color Compensating Polyester Filter) Manufacturer Code: Y40-P3. These are polyester films for doing color adjustment.
The problem is that the Seven5 75mm filter holder that they sell has slots that are wide and designed for heavy 75mm glass filters.
How do I use the holder with films? Do I just drop the film into the holder loose or is there some way to secure it in the holder with a frame of some kind?