Glue the aft tab on the lower seam of the cabin. Now is a good time to cut out the vertical tail. Bend the glue tabs outward on the vertical tail and then apply a thin strip of glue around the top and rear of the tail. Glue the port and starboard sides of the tail together and set aside to dry while you finish gluing the cabin to the rest of the fuselage.
Hopefully the seam around the vertical tail is dry now and you can stuff the rudder (furthest back end of the tail) with tissue paper to fill it out. (not shown). Be careful to not let the tissue to obstruct the holes for the horizontal tail.
Glue the vertical tail to the tail cone of the fuselage lining up the edges of the glue tabs with the faint lines on the top of the fuselage. This thing is starting to look like an Otter!