Here is my 8x10 pinhole camera, with various parameters listed. I did a little work with paper negatives back at the end of April for WPPD, and picked up some 8x10 Green Xray film early this summer, but have been too busy with other stuff to experiment further.
The pinhole constant (1.65) and f/22 multiplier are related to the use of Pinhole Designer, a Windoze based utility. The pinhole constant is a magic input typically ranging from 1.4 to 1.9 or so. The "f/22 exp multiplier" is used for metering. You read the exposure time for f/22 and then multiply it by that multiplier to get the actual exposure at the tiny pinhole aperture. (There can still be issues of reciprocity failure which may need to be dealt with.)