The holder was too short to actually fit a sheet. Removed the light trap cover by taking out the screws. Inside there is a border/stop glued in place. I actually just popped them out and switched the ends that but against the film- it looks like they were placed backwards originally since the side with the sloped overhang to hold the film edge was facing the wrong way. I used a scrap negative to gauge where to epoxy it back down and then reinstalled the cover on the light trap.