.....I think that the thin C A "wicks" into the wood. I think it makes very strong joints IF the pieces fit together very well. I think the medium and thick C A's work well if the pieces don't fit together perfectly enough to use the thin C A. But I don't think that the medium or thick C A 's "wick" into the wood very much, and thus the joint is not as strong. I would describe them as "second choice" to the thin C A....................I prefer to use epoxy to actually join wing halves. It provides the time necessary to make measurements and confirm that the two panels are properly aligned..............There is a new glue, (new to me anyway) called gorilla glue. It looks like Ambroid. It is at the hardware store. It was developed in Europe in the furniture industry. This is what I like about it: 1) non-toxic , 2) completely sandable, 3) expands as it dries, very handy when sheeting wings as a tiny fillet is formed around every rib at the point the sheeting is attached, and 4) supposedly has the strength of epoxy..........Having said all of that, I still use tried and true epoxy at the center section..............Another glue that I like is Pica's Gluit. This is a white glue that looks like Elmers glue. It is perfect for butt joining sheets together to form wing skins. Why? Because it is slightly flexible and sands well, ( no little ridges running down your wing). Another glue that I like is the RC560 glue. It is generally sold in the hobby shops for mounting canopies. However the label on the bottle suggest other uses. It is simply wonderful for mounting any plastic details to your plane. It remains slightly flexible and thus shock resistant. A little goes a long way, so buy the smallest bottle.............Oh, about the Gorilla glue, once open, the shelf life is only about six months. Again, get the smallest bottle.