The Polaroid 110A/600SE with roll film back.
Wanted a 6x9, it would be silly to stick anything less on this big brute of a camera. Since the M-adapter type backs obscure the viewfinder, and the G-type adapters only allow RB67 roll film backs, I went and made/adapted my own solution. Took an adapter probably taken off a CB-70/103 pack film back, and a Graflex 23 I went about getting the film plane right. This meant grinding out a trough 3.2mm deep in the adapter plate.
The roll film holder has no means of fixing to the adapter. So I made a skirt of 1/8" aluminium, glued it to the holder and then bolted it to the adapter. A bit of paint and light tight foam later and hey presto:
Mounted on the camera: