Anamorphic adapter on a longer telephoto lens?

[TheJay]

Has anyone ever experimented using an anamorphic adapter like Sirui 1.25x on a 200mm or longer telephoto lens? The specs shows the Sirui adapter working up to 135mm in M4/3 format and I'm curious if there would there be negative effects going longer, or do they just say up to 135mm because it would be less common to use on a longer telephoto lens?

Just curious what all of your thoughts are on this type of setup and if it would work or not  -  I would be using a GH6 with PL 200mm f2.8. 

Thanks! 

-J