I have seen ~4 ft prints from 4x5 pinhole, taken on acros. They certainly looked credible to my eye. Scott (Flying Camera) may recall who that was, hit was a photographer had a small show in DC. Federal scenes, as I recall. N.b. the final prints were not analogue and I was too polite if they were digitally sharpened, but they looked undoctored and quite effective.
Anyway, roughly speaking, at enlargements bigger than ~1:1 (contact print), the lack of detail will become evident. But that doesn't mean that the image falls apart.... if the method is suited to the subject, you can go much larger.