Good morning, Ron;
It has been a while, and no one has responded. I do not know why.
I can offer a slightly related response. While I do not have any of the sizes of roll film holders that you specifically reference, I do have an RH-8 for making 6 x 7 images on 120 roll film with a 4 by 5 camera. It has been useful, and it has served a purpose where I needed the movements of a view camera, but I could work with the limits of 120 roll film. It has been an interesting way to use 120 roll film, sort of like a 120 roll film view camera is the best way that I can describe it. Probably the main advantage is the obviously lower film cost in comparison with 4 by 5 sheet film.
I realize that this does not really answer your question about the 6 x 12 to 6 x 17 panoramic images on 120 roll film. Sorry.
Enjoy;
Ralph
Latte Land, Washington