Pentax confirms FF camera !

If you are going to build a mirrorless body then you need to go with a new mount.  The advantage to a mirrorless system is the smaller size and the only way to achieve that is to remove the OVF and shorten the register distance.

If the body is going to be the same size and use the same large lenses there is no reason to make it mirrorless.  I would rather have the OVF if I can't get a smaller camera.

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Contax 645, Canon 5D (sold), Olympus E-3 (sold), Playing with a K-7 and K-5