Totally newbie, I just purchased a 9 x 12 Voigtlander. It is in great condition and can't wait to get into the field. Never shot large format before. It came with 6 original film holders. All still contain glass negatives. Can I recondition the holders? Can the be converted to cut film sheets? It seems like there would be a lot of wiggle room for film sheets. I have read that the external dimensions of 4 x 5 film holders are the same as 9 x 12. Should I buy new holders? Will any brand do?