Perhaps I should explain a few of things. I am aware of and possess many of the options available including those once produced by Cyclopital3D. I personally use a Panasonic GX-7 with versions of the Lumix 3D lens and on occasions, a Zeiss Stereotar 842. The Stereotar out performs all other adapters I have tried, including those produced by Franc and Pentax.
I also use a Canon 5D MkII with a home made stereo adapter, similar to that once produced by Kula, using 4 first surface mirrors. I would suggest to Oktay that he follows the Kula route for the adapter, using a dedicated prime lens to match the camera. The concept of extending the stereo base of the Lumix 3D lens is a non starter in my view.
Regarding Keystone distortion, I have found that SPM corrects this very well. The bigger problem with all these adapters is the inherent narrow field of view - no wide angle potential. Fortunately, we do have the Fuji W3 and Panasonic 3D1 to work with, if they can be found.
I shall be glad to answer any questions relating to twinned rigs and their synchronisation.