I had a Koni-Omegaflax M until it was lost in a house fire c. 2004-5. The only 6x7 TLR that I know of and also the criterium that I personally use to rate the chops of reviewers who often state that the Mamiyas are the only interchangable lens TLR. Strictly speaking the Omegaflex was not a "flex" (the finder was straight through, though a reflex accessory finder was available.) I REALLY loved the eye-level chimney finder and the Hexanons, especially the 58 and 135. With the 58 I shot the original PRR GG-1 locomotive hand-held at 1/30s with the 58 wide open at the Railroad Museum of Pennsylvania. The National Engineering Landmark plaque (the size of an historical marker) was easily readable when the slide was projected.