Output Transformers

[Thatch_Ear]

I have a few of the same OPTs made by Fisher for 7591/7868 tubes in PP. They look like it wouldn't be a huge project to drop the center lams down ang get some paper in there.
Is there any paper out there, site to look at or book to buy that can give me the way for a dumbass (me) to figure out how thick I need to have the paper to get different plate loads. I once lammed a high quality audio choke for the experience, so the grains all the same, measured the paper with a micrometer etc so I have a bit of doing the whole thing, but not figuring out how thick the paper had to be, just how thick I need to get it.
Some experience in the making of, but none in figuring out how thick the paper needed to be. These is particularly strange to me because I will be working with iron made for PP, knowing that a bit of paper will let me make SE out of it. Not how well it will work, just that it should.
Who do I need to bother, I mean ask, about this?
Thatch