I don't know the design of your carrier, but if there is room in there, a thickness of tape or two will take the pressure off. I made my 5x7 carrier that way. I laid a negative on the glass and taped around the border with black photographic tape. I can't recall, but imagine it was two thicknesses. This made the negative very easy to position, and prevented newton rings even with my plain glass.
I don't know if your problem might be on the emulsion side; it seems like I had just one film type that had that issue.
What film? T-Max?
TMX-100 dries so amazingly flat, I bet I very well *could* just tape it to the single glass. I might revisit and file out a bit of my regular glassless carrier, not a fan of the marks the negaflat leaves in the image area.
Yup, TMX and Acros have emulsion surfaces shiny enough to sometimes cause Newton rings.
This makes so much sense now, I did not see them at 11x14 in a complex scene and the 12"x24" prints I made that looked perfect were from 6x12 Pan-F, a dull surface.
I looked again at my Negaflat carrier and it really does not crop as much as I thought and could even be filed out a bit if we're feeling anal about it and it does hold Tmax super flat. Still not a fan of the bite marks, but they are right at the frame edge, so that might be the ticket for Tmax films...
I have the easel blades set about 1/4 inch all around. My enlarged image area is slightly inside. The black border from my filed negative carriers outline my images, it is like the ragged 35mm style black border. The easel doesn't usually mask any edges (but sometimes just an accidental touch).
So if I used a pen flashlight, the black would "bleed" outside my printed black border.
You've solved this problem?