I think the reason to use the mutiformate back is that you can double the length of the lens when shooting 4.5X6. I agree that in the 6X9 format the lens are not slow, the comment was in relationship to 35mm rangefinder lens. In addition to the hand held tech described above you can also use a monopode. If you don't need all of the features of a Universal then a Mamyia Press with the 90mm can be a good choice.

Paul