Funny to see this pop up -- just two days ago I filed out the length of one of my Omega B8 carriers after my first attempt to enlarge a negative from my Ercona II (a "6x9") disclosed the largest carrier I had, while close in width, was only 81mm long and the camera frame is about 86. (I have no plans to print with a black border proclaiming "Fuji RVP" or any such thing.

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oh yikes. I just got a new glass carrier to print film from this camera, and it didn't occur to me that this could happen.... it should have because I had to cut a new mat board carrier and make a new easel when I first started printing from it... the frames are definitely wider than my other 6x9 folders. I got the glass carrier because the film I've been using lately is curly, but didn't think about the frame size.
Jerry's reply made me laugh. I really liked the black borders when I first started printing again, but I was after a neat thin black line, not to show that I printed the "full frame". Now if I want a black border, I make it by sliding a black cutout rectangle around inside the easel... but tastes change I guess. I haven't done that in a long time and now I like clean crisp white borders.
EDIT: just tried it and it looks like I'll lose 2mm from each end of the frame, and none at all from the top and bottom. I'm pretty sure that when I cut my matboard carrier, I used 1.5 mm all the way around, so not really much different. But important to keep in mind when composing the photo. Whew!