The internal wall is in 2 parts, the one shown in cyan on this picture and the second half also shown in cyan in picture 021. Prior to install this first half there will be a need to make some adjustments, being sure the second half is in front of the opening and the first half fits well with the original model. I had to sand quite a lot of the original Command Module shell to be sure it would fit. Once this is done this first half in cyan will help you as a pattern to cut an opening in the CM shell for the hatch.