I believe that special sizes (not 8x10 or 11x14) Centennial POP is only made by special order and only at s certain time of year. I doubt you'd be able to order just a few sheets of it. But if so, you'd need to contact Chicago Albumen directly and ask about it. B&S doesn't have it listed.
My understanding is that 20x24 is a standard size according to CAW website. I just don't want to buy a box of 25 sheet for almost $200 yet...
I am just simply using them for my 7x17 negatives (by making 3 8x20 out of one sheet). I do not have an access to 20x24 camera. Though I think I saw it at 68 degrees though...
If you are looking for a Momuth plate camera good luck as I undestand it ther is 2 or 3 people that have such cameras in the west coast one is Patrick Alt at
altview.com He may be able to build one but you are talking BIG BUCkS
and that is if you can talk him into building one , maybe 10K if not more
I built my own 20x24 camera for under $1500. The film holders are a different issue. Check out my post dated 9-30-05 in the camera building and modification seciton of apug. It is posted under "Buulf Cameras". Buulf stands for Butt Ugly Ultra Large Format Camera.
I posted pictures of my 16x20, but the 20x24 is the same design and only slightly larger. I can post pics of the 20x24 if you need.