Good quality roll film backs for view cameras are plentiful and cheap on the S/H market. For the price of that adapter I would rather get one or two 6x7 Horseman roll film backs and crop down to 6x6. OTOH, shooting rollfilm on a 4x5 with view camera lenses is a compromise as such, and I personally don't see the point in shooting anything smaller than 6x9 on a view camera. So if I wanted to shoot square format on a view camera I would probably rather use 4x5 sheets and crop accordingly.