I have had this image in mind since September, and was originally thinking of using my Linhof Kardan camera (4"x5"), but in the end used Bronica GS-1 (6x7) instead, as that's the biggest camera I can practically carry on my bike.

Scan of a 14"x7" (plus 1" margin) silver gelatine test print; the 'real' print is 18"x9".