Arca Swiss made a 6x9 too; just seen one for sale in the Sept/Oct 2012 edition of The Photographic Trader (alas no longer printed!). $800 for the camera, 2 bag bellows, 6x6, 6x7, 6x9 backs and reflex viewer (lenses were additional), but I think the suggestion to go for a 5x4 and use a 6x9 back, could work out better; "more bang for your buck" so to speak.