Probably you should seek for the Cokin A series instead?
The P adapter will work, but adds unnecessary girth and thereby handling awkwardness to the modified lens. One could of course Dremel down the Cokin, but as shown below, not much would be gained in overall slimness as long as the K-rings are deployed.
Below is the 100/1.6 in the "minimum" configuration with K4, K5, and K2 added. This combination of extension provides a bayonet just clearing the rear element so is about the shortest you can have with an "F" mount camera. For m43 or similar, you need something that will accommodate the naked rear end within it to allow focusing farther away, perhaps even to infinity if the contraption is short enough.
(this is from the first stage with the 100/1.6 so the CPU hasn't been added yet. It will fit nicely inside the K2, though)