The Zuiko 7-14/2.8 PRO w/ Lee filters.
The filter holder closest to the lens is a Lee holder fitted w/ the slimmer Shapeways Kit II filter slots, and the outer holder is an original Lee holder (unchanged), w/ a rotating ring underneath it.
This way both filters can rotate freely. Here seen w/ a 100x100 mm Lee CPL filter in the Shapeways slots (for the sake of illustration not fully inserted here), and a Lee ND 0.3 filter in the original Lee slots.
In my experience this stacked combo does not vignette with any filter rotation when using a focal length of 8>8.5 mm or longer.
At 7 mm there's no vignetting with leveled filters, and still minimal w/ rotated filters, no more than easily fixed in post.
To mitigate vignetting further, the outer filter slot may be removed on the outer holder (Lee slots can be added/removed one by one), even though the holder will take just one single filter that way.