For a better raw stream I would recommend you enable the 5K anamorphic flv preset and Ratio to OFF. Now you can work with the full sensor readout. Next if you want to modify fps I have created a function called 5k anamorphic flv TL. Using that you can go from 1-14 to modify fps. For instance set it to 14 and you´,ll get 1.5fps. If you also enable shutter range to Full range you shutter will go down all the way to 0.6.
A little tricky to do alla of this but you can save all your settings into custom preset and access it easy the next time you use it. Also turn off audio recording for best performance.
