I had to fill a small part of where the rear access cover fastens to the fuselage. When I made the ribs that fit inside the vertical tail it calls for a small L shaped piece of aluminum to be attached so that the access cover can be attached to the fuselage. I attached mine flush with the ribs thinking that would then be flush once installed. Once it was made I realized that the rib was not as wide as the fuselage and therefore the aluminum was not going to be far enough out. To fix this the only thing I could come up with was to apply superfill to the area as needed. It seems to have worked out OK I guess time will tell. I also started making an attachment point for the two covers where the braces coming from the fuselage attach to the horizontal stabilzer. The kit comes with a reinforcement plate that attaches to the fabric and then you secure the cover to the reinforcement plate. I decided that I wanted somthing a little stronger which is why I am going this route.