I have (I think) a Beseler 45MX, the blue one, and the filter tray that goes above the negative is included. However, it's not obvious how a 6x6 filter sits in it. It's just a thin metal frame that slips into the drawer and is shaped like a half-circle on the back end. Am I missing a piece? I've tried to look for a photo of it all over the place so I can compare, but no luck!
If I trim the filter to fit the opening, it won't cover the whole open space in the frame. See my crude 25 second drawing attached Should the open space be masked with black mat or something?