Great advice, all.
I'll add that there's a tradeoff between wanting an ultra-high focal ratio for intended sharpness and then losing that sharpness with the extra-long exposure times and possible camera movement blurring the image. Focal ratios around f/150-250 are often satisfying, of course depending on format size and focal length.
Larger sized formats will also give you more information and perceived sharpness, since the negatives can usually be contact printed rather than enlarged, and there's more information present if scanning.
Also, tonal range is at least as important to me as sharpness. Good tones, good composition and interesting subject matter are all more important to me than mere sharpness. In the end, a pinhole camera is still a camera, and thus all the essential elements of a good photograph are still required.
Looking forward to seeing more of your work.