John Wiegerink
Subscriber
I have the deluxe chimney finder, but don't really use it much. As far as interchangeable backs? I have and use several model Zeiss Contaflex cameras and have several of the interchangeable back that work on it and the Zeiss Contarex cameras. Those backs don't increase the size and weight of the camera much at all. The only drawback to those backs is a leaky dark slide slot after they age. I'd suffer just a little extra size and weight just to have interchangeable backs on the Pentax 67, but we all know that's certainly wishful thinking.The P67 prism is what mostly makes it heavy. Having a 100% size one would make it even worse in that respect. The deluxe chimney finder does provide 100%, plus brighter viewing and more critical focus, but not eye-level use or convenient vertical composition.
And if it had interchangeable backs, there would go all the "big brother to 35 mm" ergonomic handling the P67 is prized for. Every system involves certain compromises.