I am not sure what I will end up with, but there is no need to gouge out the ribs.
If one uses a D-subminiature 9-pin female and mount the flange on the outside of the
box, and fasten it with two Hex "Jack Screws" into two nuts inside, the hole cutting
(after drillig several holes) is not too bad.
But, it makes the box look a bit ugly, there on the side, but it would be very finctional.
What do you think?