In Windsock Datafile 93, there are a couple of pictures (pages 6 and 9) of a cylindrical wire cage for dropping the Carbonit bombs, just behind the radiators. There is a space between the lower wing and fuselage at the rear. The cage is mounted between the two cockpits, and the observer might be able to turn around and reach it. in the photo on page 6, it looks like there could be a wire from the top into the cockpit, perhaps for a release mechanism. The two pictures look like slightly different designs, so may have been fabricated at the unit level.
Rich