CPL options for the new E10-18

Hi I think I will be getting my E10-18 any time before this year ends, but I am not quite sure what to start with when it comes to CPL for ultra wide lenses. I used to own an ultra wide (sigma 8-16) which did not get along well with any filters since the front element of the lens is a sphere-like design. I would like to get some general ideas about what to choose from for the E10-18. Does it have to be slim in order to avoid vignetting? Would the normal side CPL be okay?

Thank you