That must be the ultimate camera obscura, an humungous 8x20, and it looks very well engineered, too! I do like the ultra-wide view and definition does appear good (assuming no sharpness has been applied by Photochopping!). I agree with your comment regarding a perceived lack of "pinhole funk" (there goes a term with clout!); I don't want my pinhole images to exhibit the razor sharpness of my Canon L-series optics!
I will shortly be changing the format in my Zero Image from 6x6 to the "ultra-wide enough for me" 6x9.
Efke sounds like an interesing film in the old classic mould, but my Pro lab was unaware of the need for a hardener to be applied (or somesuch) due to its perceived "frailty".