I had this notion that as you go off axis from the center of the pinhole projected onto the film, the area of the pinhole would decrease, necessitating a shorter focal length to maintain exposure.
I am not one to engineer things, and I certainly dislike math, but sometimes one must do what one must do.

It tuns out the ideal pinhole camera for consistent exposure is a sphere. A cylinder will have to do for photo paper.

Here is an exposure in a paint can