theo63,
I build a little differently than most people do. When I build I like to completely build the plane before I cover it, and that included gluing the horizontal and vertical stabilizer. I will also glue the control surfaces on before I cover too. But before I glue the control surfaces in place I will cover the ends of the control surfaces. The reason I like to assemble first is that I absolutely hate cutting into a covering job to add weight to balance the plane. So I will completely assemble the plane (with the exception of the covering of course) and then balance the plane, then cover the plane, and recheck the balance after the plane is assembled again. Sometimes the plane needs a little bit of adjustment in the balance after being assembled but that can usually be accomplished by moving the receiver and battery location. When it comes to covering I do put a small strip of the covering where the surfaces meet and the cover over that, see the included pictures to get an idea of what I'm talking about.

As I said above I also glue the control surfaces before I cover, and then I will actually cover and seal the gap. I do this for two reasons. One is that the covering seals the gap which improves the performance of the plane. Second, sealing the gap (especially when using CA hinges) will help prevent failure of the hinges. In essence when the gap is sealed with covering you now have two types of hinges, CA and covering hinges, which makes for a more reliable plane. When sealing the gap I will use a strip of covering folded in half and placed in the gap between the control surface and the trailing edge that it's attached to, then heat the covering to seal it in the gap, and finally sealing the edges of the covering to the control surface and the opposite trailing edge. Then when covering those surfaces cover right up to the gap.

Hopefully these pictures will help explain a little bit better.

Ken