You got it. If the holder has a a removable film sheath, you can take it out and use a 9x12 plate. I'd love to shoot some plates at some point, but not wet ones--I like my 9x12 camera too much. I've seen some ancient 9x12 dry plates on ebay and Slavich used to make them--not sure if they're still in production. You could ask at Laser Reflections--they're one of the only US Slavich resellers.