panoramic pei

The whole idea behind this: is to create a true panoramic format, as a Hasseblad Xpan for example. Cropping 120 film is not a true panoramic format. This actually worked out well with an earlier S Motorized Back, although I abandoned the project a few years ago due to the collective weight with a heavy duty tripod in the field. Presently photographing with a Fuji GSW690 III, modified for 35mm film produces a 24mm x 80mm panoramic format frame. Some images here:

I was wondering if anyone has loaded a Mamiya RB 120/220 Motorized Back 6x8 or 6x7 with 35mm film with successful results? The 6x8 Back I have functions perfectly with 120 film in manual or motorized, tested with a test dummy 120 film. When I load a 35mm dummy film 24 exposures with the plate on 120 or 220, the film will not stop on 1, in manual or with the motor, it just keeps advancing until the 35mm roll is finished. I can't seem to find the catch, latch or pin or whatever detects the 120 film is loaded & stops at #1. I know this can be done easily with a normal 220 Back although I really wanted the 6x8 format, not necessarily the motor.