- First , I removed two sides of the supplied foam from the box, i.e. the box has the "bottom" foam, and a short and long side foam-- One of the short and long sides was removed.

    - I Put the mount in with the RA and Saddle in the “park 3” position.

It seems to fit in the box with just a bit of room to spare. Maybe an inch.

Since the interior of the iM2875 is about an inch bigger in w x h I would expect there is some room for foam all around.
iM2875 = 22.5 x 21.1 x 11.4
AP Box  = 21.5 x 19.5 x 11.25

So.. it seems it will fit this way in the iM2875.

Also... fwiw.. I don't really want to add additional things to the mount case.   It will become too heavy to get out of the car.

Currently the mount is IIRC 40 lbs , iirc w/o cw shaft.

These cases are like 20 lbs.

I could see stashing some things in the case when it is already in the car, but the trunk arrangement will make it difficult to open the box.