Plate holders arrived from England, two of them. They fit the 12x15 camera. Well, they will fit it with a little fussing. They are both most exactly the same size, being just a little larger here and there. A little sanding, glue, tape, a hinge, paint inside, well, more than a little fussing is required. Beggars can't be choosers. You just can't get holders this size very often. They are older and more beat up than the nasty 10x12 what needs work. Very well. Glad to have 'em both.
The 11x14 puddle pusher may work for 12x15 plates if a dowl rod is inside the glass tube and the ends of THAT rod are built up with tape. Anything larger is a special order and costs much more. I can try to make what I got work.
Three new 19th century books were downloaded from Google books. Now I've got to read three web sites and three old books. No problem. One book has plans on how to construct drying cabinets for plates or for papers. Just what I need. The source is the article written by Ms Ross for The Light Farm located in Articles.