Making a size reducing mask for a Durst 138 neg carrier.. 6x7 > 6x6

I have acquired a Durst 138 Laborator and I have all the LAPTE neg holders for the different formats from 35mm > 5x7, except 6x6. But I do have a 56x72 neg holder. I shoot 6x6 and want to use 56x72 for the 6x6. I store my 6x6 negs in strips of three negs. All the neg holders I have have 6 pins on one plate that register with holes in the top plate. Needless to say, the two pins, one at each end, are in the way of my strip. I want to remove those pins. Would removing those 2 pins cause any kind of problems? There are still the 4 pins , at top and bottom to hole the plates in register.

Since I'm on it, I want to reduce the hole from 56x72 to 56x56, in order to eliminate the extraneous light. I was thinking that a strip of sheet film, glued under the the top plate, would reduce the light considerbly and yet thin enough to sit between the plate and the film.

Any suggestions?

Get a sheet of Rubylith from an art's supply store. This is a thin sheet of transparent red plastic which ca n easily be cut to size with a box cutter or Exacto knife. You can use a paper puch to make the pin holes. The red color will prevent any spillover of white light. I would not recommend permanently gluing any mask to the carrier as this would decrease its value.

Thanks for the wake-up call. Reading your post made me realize I have a roll of the stuff... I bought it to make a mask for my computer screen which is now installed in my darkroom. I'll make holes with a hole puncher and tape the edges to the plate. I have to tape it since I just tried it and the puncher makes a holes that leaves room for play. I can put it on the bottom plate since the idea is to eliminate extraneous light.

Thanks!