I wouldn't argue that I was rigorously scientific in my approach, but my first pinhole efforts were done using a pinhole lensboard in my B&J Press camera, that allowed me to play around adjusting the lens-to-film distance with a given pinhole. I settled on a 0.46 mm pinhole at about 165 mm spacing (approx f360).

More recently, I built an elaborate "box camera" to use a 4x5 holder. For that I used a pinhole of about 0.305 mm at a distance of 63 mm (approx f210) to produce a fairly wide angle of coverage.

The joy of these beasties is that the variations appear to reflect very broad curves in the functions, and a wide range of choices can work pretty effectively. A variable most tedious to control is the quality of the pinhole itself. Ideally it has a knife edge and the opening is perfectly round with no ragged imperfections. This accounts for the popularity of laser-cut pinhole plates. But I must say this latest one of mine, built for last April's Worldwide Pinhole Photography Day and using a sanded dimple in one-mil brass shim stock, produced the best results I've had yet (maybe I just got lucky!)