Chuck;
I've done lots of pinhole, on lots of different papers (but certainly not all of them). Here's my thoughts on achieving the best sharpness and tonal range with pinhole:
1)Optimal pinhole size for your focal length. This is especially important if you're trying to get scenic/landscape shots to look reasonably sharp. And if your primary subject matter is much closer than infinity - like still life subjects - make the pinhole smaller than what you'd use for objects near infinity (because the geometry of linear projection works against you at close focus distances).
2)For flat film-plane cameras (i.e., not oatmeal boxes with curved film planes), use GLOSSY paper. Glossy will give you much sharper contact prints. If the inside of the camera is darkened with flat black paint, glossy paper won't be a problem with flat-filmplane cameras.
The problem with curved filmplane cameras is you have to use matte finish paper, otherwise you get a band of over-exposure along the middle of the film's curve, due to reflection. You loose a lot of detail when trying to contact print from a matte-finish negative, which is one reason I rarely dabble in curved-filmplane cameras.
3)Contrast control in harsh lighting is difficult with paper negatives. I like to shoot scenics in the American Southwest, but the shadows are very harsh and unforgiving.
My best results to date: grade 2 glossy paper. Specifically, Arista grade 2 RC, but any graded paper should work better than multi-grade paper. My gut feel is its the blue/UV in daylight that activates the high-contrast portion of the MG emulsion, yielding images difficult to print.
As for using fiber based for negatives, that's okay. Its better if its graded paper, but fiber is okay - in fact, graded fiber has a slightly better tonal range then graded RC. The only challenge you'll have is it tends to curl toward the emulsion side, so getting it into your contact printing frame, against the print paper, can be a challenge, especially if registration and positioning are important.
4) This week I've been experimenting with controlled pre-flashing of paper negatives, as a way to control contrast. I pre-flashed some paper under a grade 3 filtered light, underneath a sheet of white plexiglass, in the darkroom for 2 second, then exposed an outdoor image that otherwise would have zero shadow detail (we're talking paper white shadows, absolutely nothing) in the pinhole camera for about 1/2 of its normal daytime exposure (~30 seconds). The result: amazingly good shadow detail, with good highlight detail as well. The contrast range is really good for such a wide scene brightness range, onto paper negative.
One cavaet: when I pre-flashed the paper, I did so with the paper face down, under the sheet of plexiglass, because face-up pre-flashing was just too much light (it fogged it to black otherwise). The resulting shadow detail in the paper negative looked very "grainy" or "clumpy". I think this was caused by the grain of the paper that the pre-flash lighting has to filter through.
I'm going to do some more experiments with pre-flashing from the front of the negative, and see if the graininess in the shadows goes away.
I also have a hunch that you can achieve even more control of the paper's response curve by controlling at what contrast grade the pre-flashing light is filtered to. This, however, will involve lots of testing to verify and quantify.
SUMMARY: 1) Optimal pinhole size for your camera's focal length. 2)Flat film-plane camera. 3)Graded glossy paper (RC is okay). 4)Pre-flash the paper for additional control of contrast.
