Glad to see some activity on paper negatives. I like them a lot in large format cameras and are always amazed about the quality of the contact prints. Makes me feel like Fox Talbot. I use Ilford MGIV-RC with a yellow filter (Wratten #8) and rate the paper at EI 3, but I don't flash or fog the paper at all. For development, I use Dektol 1+8 and develop to a Dmax around 1.2. The filter and the dilute developer control the contrast nicely.
I never had an issue with the filter showing in pinhole photography, and judging from the calculations, it shouldn't. The filter is just too close to my pinholes, which are around f/256.