Thanks for your reply Rolando,
yes you are right about the the kowa - it has a 54mm screw mount and a 70mm front element, I'm using step down ring, then a polarizer with the glass taken out to orient the anamorphic lens - and there will be vignetting at shorter focal lengths because of the difference in lens area + adapters, etc. I just need to do some tests with it. But kudos for your custom design!