I use filed out negative carriers and some time anti-Newton glass carriers. With the filed out carriers I use low tack White paper tape to hold the film in place and cut the piece in half with pinking shears to create teeth on either edge and attach the tape about half way into the sprocket holes and in the center of the frame edges. This holds the film in the carrier but doesn't show in the rebate that winds up as part of the print.The low tack tape's adhesive doesn't come off on the film. My anti-Newton glass carrier is a Beseler 4x5, I cut a mask to center the neg and eliminate any flare that can be caused by the clear surrounding glass, which allows me to tape the film strip to the mask. Hope that's useful information!
Bill